Add blueprints for authentication, admin, dashboard, gallery, generation, and profile routes

- Created `__init__.py` for blueprint registration.
- Implemented `auth.py` for user authentication (login, register, logout).
- Added `admin.py` for admin functionalities (user management, stats).
- Developed `dashboard.py` for user dashboard displaying user info and generated content.
- Created `gallery.py` for managing and displaying images and videos.
- Implemented `generate.py` for text, image, and video generation functionalities.
- Added `profile.py` for user profile management.
- Updated templates to reflect new route structures and improve navigation.

frontend/app/templates/admin.html

@@ -42,7 +42,7 @@
               <!-- Role toggle -->
               <form
                 method="post"
-                action="{{ url_for('admin_set_role', user_id=u.id) }}"
+                action="{{ url_for('admin.set_role', user_id=u.id) }}"
               >
                 <input
                   type="hidden"
@@ -57,7 +57,7 @@
               {% if u.id != session.get('user_id') %}
               <form
                 method="post"
-                action="{{ url_for('admin_delete_user', user_id=u.id) }}"
+                action="{{ url_for('admin.delete_user', user_id=u.id) }}"
                 onsubmit="return confirm('Delete {{ u.email }}?')"
               >
                 <button type="submit" class="btn btn-sm btn-danger">