Added full message handling system with archive view, pagination, and send support

- Implemented message inbox and archived messages view
- Added pagination logic to both inbox and archive handlers
- Integrated message sending functionality with CSRF protection
- Updated schema to include `archived_at` timestamp
- Included archive button and logic with feedback flash messaging
- Fixed message dropdown routing and rendering in topbar
- Cleaned up template load paths and error handling

models/user.go

@@ -30,6 +30,7 @@ type Message struct {
 	Message     string
 	IsRead      bool
 	CreatedAt   time.Time
+	ArchivedAt  *time.Time
 }
 
 var db *sql.DB