Replace emoji icons with local SVG files for consistent rendering

- Created 10 SVG icon files in app/static/icons/ (Feather Icons style)
- Updated base.html with SVG icons in navigation and dark mode toggle
- Updated dashboard.html with icons in stats cards and quick actions
- Updated content_list_new.html (playlist management) with SVG icons
- Updated upload_media.html with upload-related icons
- Updated manage_player.html with player management icons
- Icons use currentColor for automatic theme adaptation
- Removed emoji dependency for better Raspberry Pi compatibility
- Added ICON_INTEGRATION.md documentation

app/models/__init__.py

@@ -2,6 +2,7 @@
 from app.models.user import User
 from app.models.player import Player
 from app.models.group import Group, group_content
+from app.models.playlist import Playlist, playlist_content
 from app.models.content import Content
 from app.models.server_log import ServerLog
 from app.models.player_feedback import PlayerFeedback
@@ -10,8 +11,10 @@ __all__ = [
     'User',
     'Player',
     'Group',
+    'Playlist',
     'Content',
     'ServerLog',
     'PlayerFeedback',
     'group_content',
+    'playlist_content',
 ]