feat: Implement in-app notifications with new database model, enhance Firebase initialization to support service account files, and add message read functionalities.

prisma/schema.prisma

@@ -132,6 +132,9 @@ model User {
   conversations     Conversation[]
   messages          Message[]
 
+  // Notifications
+  notifications     Notification[]
+
   @@index([email])
   @@index([role])
   @@index([status])
@@ -500,6 +503,31 @@ model Message {
   @@map("messages")
 }
 
+// ===========================================
+// IN-APP NOTIFICATIONS
+// ===========================================
+
+model Notification {
+  id          String   @id @default(uuid())
+  userId      String
+  type        String   // 'connection', 'message', 'system', 'update', 'request'
+  title       String
+  description String
+  read        Boolean  @default(false)
+  actionUrl   String?
+  data        Json?    // Extra metadata (conversationId, connectionRequestId, etc.)
+
+  // Timestamps
+  createdAt   DateTime @default(now())
+
+  // Relations
+  user        User     @relation(fields: [userId], references: [id], onDelete: Cascade)
+
+  @@index([userId, read])
+  @@index([userId, createdAt])
+  @@map("notifications")
+}
+
 // ===========================================
 // CMS CONTENT - Dynamic page content management
 // ===========================================