feat: implement tenant branding system and global toast notification service

src/app/shared/components/toast-container/toast-container.component.scss

@@ -0,0 +1,28 @@
+.toast-container {
+  z-index: 1500;
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  pointer-events: none;
+
+  .toast {
+    pointer-events: auto;
+    min-width: 300px;
+    max-width: 450px;
+    border-radius: 8px;
+    animation: toast-slide-in 0.3s cubic-bezier(0.16, 1, 0.3, 1) forwards;
+    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.15), 0 4px 6px -4px rgba(0, 0, 0, 0.15) !important;
+    transition: all 0.2s ease-in-out;
+  }
+}
+
+@keyframes toast-slide-in {
+  from {
+    opacity: 0;
+    transform: translateY(-20px) scale(0.95);
+  }
+  to {
+    opacity: 1;
+    transform: translateY(0) scale(1);
+  }
+}