Squashed commit of the following:

commit cd99a6489b
Merge: ebcbbb1 e63a036
Author: ncoronel <ncoronel@quo.ar>
Date:   Wed Aug 26 10:12:44 2026 -0300

    Merge branch 'fix/simplify_stock_reservations' of https://gitea.quo.ar/tbianchini/shopit-back into fix/simplify_stock_reservations

commit ebcbbb1774
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:33:39 2026 -0300

    fix(cart): reconcile expired cart mutations

commit 3dd378ed06
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:10:15 2026 -0300

    docs(stock): describe associated entity expiration

commit 4f705175bd
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:10:14 2026 -0300

    test(stock): cover propagated reservation expiration

commit 82570fe941
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:09:52 2026 -0300

    refactor(stock): propagate reservation expiration

commit d2a2b323e0
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:47 2026 -0300

    docs(stock): document terminal reservation recovery

commit ec67623b7b
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:47 2026 -0300

    test(stock): cover terminal reservation lifecycle

commit f6f138e180
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:41 2026 -0300

    refactor(stock): make expired reservations terminal

commit d612b7a118
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:30 2026 -0300

    docs(stock): describe unified expiration ownership

commit 49f42d4507
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:23 2026 -0300

    test(stock): cover authoritative reservation expiration

commit 1881cc1d4b
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:17 2026 -0300

    refactor(stock): make reservation expiration authoritative

commit 00ec37d8a0
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:34 2026 -0300

    docs(stock): document centralized reservation flow

commit d9f374c718
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:29 2026 -0300

    test(stock): cover aggregate reservation lifecycle

commit bbfdf8f342
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:23 2026 -0300

    refactor(stock): centralize reservation aggregate

commit 8a0f29bdae
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:33:39 2026 -0300

    fix(cart): reconcile expired cart mutations

commit 198ed400a9
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:10:15 2026 -0300

    docs(stock): describe associated entity expiration

commit 23d83166e6
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:10:14 2026 -0300

    test(stock): cover propagated reservation expiration

commit cb090402d0
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:09:52 2026 -0300

    refactor(stock): propagate reservation expiration

commit c120b6f7c0
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:47 2026 -0300

    docs(stock): document terminal reservation recovery

commit 1106fa28b4
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:47 2026 -0300

    test(stock): cover terminal reservation lifecycle

commit 896fb81bcf
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:41 2026 -0300

    refactor(stock): make expired reservations terminal

commit 8545fbc645
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:30 2026 -0300

    docs(stock): describe unified expiration ownership

commit dd6dcb708a
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:23 2026 -0300

    test(stock): cover authoritative reservation expiration

commit 624b246ff5
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:17 2026 -0300

    refactor(stock): make reservation expiration authoritative

commit 007b95b904
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:34 2026 -0300

    docs(stock): document centralized reservation flow

commit 0b3c8c93be
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:29 2026 -0300

    test(stock): cover aggregate reservation lifecycle

commit ede718e448
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:23 2026 -0300

    refactor(stock): centralize reservation aggregate

commit e63a03601a
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:33:39 2026 -0300

    fix(cart): reconcile expired cart mutations

commit 389373ad8c
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:10:15 2026 -0300

    docs(stock): describe associated entity expiration

commit ace02a3133
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:10:14 2026 -0300

    test(stock): cover propagated reservation expiration

commit d69a6210f6
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:09:52 2026 -0300

    refactor(stock): propagate reservation expiration

commit 3c0b43fea3
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:47 2026 -0300

    docs(stock): document terminal reservation recovery

commit 9b0008626b
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:47 2026 -0300

    test(stock): cover terminal reservation lifecycle

commit 61861e331a
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:58:41 2026 -0300

    refactor(stock): make expired reservations terminal

commit 2cc9d7dd97
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:30 2026 -0300

    docs(stock): describe unified expiration ownership

commit f982bcead1
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:23 2026 -0300

    test(stock): cover authoritative reservation expiration

commit 7a85e1731d
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:28:17 2026 -0300

    refactor(stock): make reservation expiration authoritative

commit 6db99e775a
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:34 2026 -0300

    docs(stock): document centralized reservation flow

commit e5f7ba3615
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:29 2026 -0300

    test(stock): cover aggregate reservation lifecycle

commit 24bfef431b
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 15:05:23 2026 -0300

    refactor(stock): centralize reservation aggregate

app/Domains/Purchase/Services/Checkout/StartCheckoutService.php

@@ -4,6 +4,7 @@ namespace App\Domains\Purchase\Services\Checkout;
 
 use App\Domains\Cart\Models\Cart;
 use App\Domains\Cart\Models\CartItem;
+use App\Domains\Catalog\Exceptions\StockReservationExpiredException;
 use App\Domains\Catalog\Models\CatalogItem;
 use App\Domains\Catalog\Models\Variant;
 use App\Domains\Catalog\Services\CatalogInventoryService;
@@ -12,6 +13,7 @@ use App\Domains\Purchase\Exceptions\InsufficientStockException;
 use App\Domains\Purchase\Models\Purchase;
 use App\Domains\Purchase\Services\UserPurchaseLimitService;
 use App\Domains\Tenant\Models\Tenant;
+use Illuminate\Support\Carbon;
 use Illuminate\Support\Collection;
 use Illuminate\Support\Facades\DB;
 use Illuminate\Validation\ValidationException;
@@ -169,21 +171,31 @@ class StartCheckoutService
                 'cantidad' => $line['quantity'],
             ]);
 
-            try {
-                $this->reservations->reserve($cartItem, $line['selection'], $line['quantity']);
-            } catch (\InvalidArgumentException) {
-                $availableQuantity = $this->inventory->availableQuantity($line['selection']) ?? 0;
-
-                throw new InsufficientStockException([
-                    $this->unavailableItem($line, $availableQuantity),
-                ]);
-            }
-
             $cartItem->setRelation('catalogItem', $line['catalog_item']);
             $cartItem->setRelation('variant', $line['selection'] instanceof Variant ? $line['selection'] : null);
             $cartItems->push($cartItem);
         }
 
+        try {
+            $this->reservations->syncCart($cart);
+        } catch (\InvalidArgumentException) {
+            $unavailable = $resolvedLines
+                ->map(function (array $line): ?array {
+                    $availableQuantity = $this->inventory->availableQuantity($line['selection']);
+
+                    return $availableQuantity !== null && $availableQuantity < $line['quantity']
+                        ? $this->unavailableItem($line, $availableQuantity)
+                        : null;
+                })
+                ->filter()
+                ->values()
+                ->all();
+
+            throw new InsufficientStockException($unavailable !== [] ? $unavailable : [
+                $this->unavailableItem($resolvedLines->first(), 0),
+            ]);
+        }
+
         $purchase = $this->createPurchase(
             $tenant,
             $userId,
@@ -194,19 +206,12 @@ class StartCheckoutService
             $cart->getKey(),
         );
         $cart->update(['current_purchase_id' => $purchase->getKey()]);
+        $this->reservations->attachToPurchase($cart, $purchase, $this->checkoutExpiration());
 
         $cartItems = $cart->items()->orderBy('id')->lockForUpdate()->get();
         $this->loadCartItems($cartItems);
         $purchase->items()->createMany($this->snapshots->fromCartItems($cartItems));
 
-        foreach ($cartItems as $index => $cartItem) {
-            $this->reservations->attachToPurchase(
-                $cartItem,
-                $resolvedLines->get($index)['selection'],
-                $purchase,
-            );
-        }
-
         return $this->loadPurchase($purchase);
     }
 
@@ -257,6 +262,7 @@ class StartCheckoutService
         $this->verifyTenantItems($tenant, $cartItems);
         $this->assertCartPurchaseLimits($tenant, $userId, $cartItems, $cart->getKey());
         $cart->setRelation('items', $cartItems);
+        $this->reservations->syncCart($cart);
 
         $purchase = $this->createPurchase(
             $tenant,
@@ -266,16 +272,9 @@ class StartCheckoutService
             $cart->getKey(),
         );
         $cart->update(['current_purchase_id' => $purchase->getKey()]);
+        $this->reservations->attachToPurchase($cart, $purchase, $this->checkoutExpiration());
         $purchase->items()->createMany($this->snapshots->fromCartItems($cartItems));
 
-        foreach ($cartItems as $cartItem) {
-            $this->reservations->attachToPurchase(
-                $cartItem,
-                $cartItem->selectedItem(),
-                $purchase,
-            );
-        }
-
         return $this->loadPurchase($purchase);
     }
 
@@ -316,9 +315,9 @@ class StartCheckoutService
             Purchase::STATUS_CREATED,
             Purchase::STATUS_PENDING_PAYMENT,
         ], true)) {
+            $this->reservations->returnToCart($currentPurchase, $cart);
             $currentPurchase->update([
                 'status' => Purchase::STATUS_SUPERSEDED,
-                'expires_at' => null,
             ]);
         }
 
@@ -331,7 +330,11 @@ class StartCheckoutService
             throw new NotFoundHttpException('Cart not found for tenant.');
         }
 
-        if ($cart->status !== 'active') {
+        if ($cart->status === Cart::STATUS_EXPIRED) {
+            throw new StockReservationExpiredException;
+        }
+
+        if ($cart->status !== Cart::STATUS_ACTIVE) {
             throw ValidationException::withMessages([
                 'cart_id' => __('api.purchase.inactive_cart'),
             ]);
@@ -405,13 +408,17 @@ class StartCheckoutService
             'user_id' => $userId,
             'status' => Purchase::STATUS_CREATED,
             'payment_method' => null,
-            'expires_at' => now()->addMinutes(
-                max(1, (int) config('purchase.checkout_expiration_minutes', 30)),
-            ),
             'total' => $total,
         ]);
     }
 
+    private function checkoutExpiration(): Carbon
+    {
+        return now()->addMinutes(
+            max(1, (int) config('purchase.checkout_expiration_minutes', 30)),
+        );
+    }
+
     /** @param Collection<int, CartItem> $cartItems */
     private function loadCartItems(Collection $cartItems): void
     {