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/app.py

@@ -62,6 +62,7 @@ def register_blueprints(app):
     from app.blueprints.players import players_bp
     from app.blueprints.groups import groups_bp
     from app.blueprints.content import content_bp
+    from app.blueprints.playlist import playlist_bp
     from app.blueprints.api import api_bp
     
     # Register blueprints (using URL prefixes from blueprint definitions)
@@ -71,6 +72,7 @@ def register_blueprints(app):
     app.register_blueprint(players_bp)
     app.register_blueprint(groups_bp)
     app.register_blueprint(content_bp)
+    app.register_blueprint(playlist_bp)
     app.register_blueprint(api_bp)