feat(auth): implement Google OAuth integration with user authentication and token exchange

database/migrations/2026_07_22_000000_add_google_id_to_users_table.php

@@ -0,0 +1,23 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('users', function (Blueprint $table): void {
+            $table->string('google_id')->nullable()->unique()->after('email');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('users', function (Blueprint $table): void {
+            $table->dropUnique(['google_id']);
+            $table->dropColumn('google_id');
+        });
+    }
+};