refactor(web): remove the two Fonts-tab panels that reported invented data

"Element Font Overrides" let a user configure an override, showed a
success toast, and changed nothing. All three endpoints behind it were
stubs -- GET returned a hardcoded {}, POST and DELETE returned success
without calling anything -- each marked "This would integrate with the
actual font system".

Wiring them to FontManager would not have fixed it. The machinery there is
real (_load_overrides/_save_overrides persist config/font_overrides.json,
resolve_font applies them, and the countdown plugin genuinely consumes
it), but the panel's element dropdown offered eleven invented keys --
nfl.live.score, clock.time, weather.current -- that no plugin has ever
read. An override saved against one of those would have persisted
correctly and still done nothing.

"Detected Manager Fonts" goes for the same reason. It claimed to show
"fonts currently in use by managers (auto-detected)"; its own comment said
"we'll simulate this", and it listed every font in the catalog with a
hardcoded usage_count of 1 -- the panel beside it, with fabricated
numbers attached.

Per-element font choice now lives in each plugin's own config editor,
against the elements that plugin actually has, and covers size, colour,
offsets, visibility, alignment and scale rather than family and size.

Kept: the font library (upload, preview, delete), which works, and
/fonts/tokens, which is a stub but genuinely feeds the preview's size
dropdown. FontManager's override methods are untouched -- countdown uses
them.

Verified in a browser with the tab's JS running: no console errors, 35
fonts listed, upload and preview intact. Removing the panel meant unwiring
it from populateFontSelects too, which would otherwise have bailed out
early on the missing select and left the preview dropdown empty.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web_interface/blueprints/api_v3.py

@@ -6809,42 +6809,6 @@ def get_font_tokens():
         logger.error('Unhandled exception', exc_info=True)
         return jsonify({'status': 'error', 'message': 'An error occurred; see logs for details', 'details': describe_exception(e)}), 500
 
-@api_v3.route('/fonts/overrides', methods=['GET'])
-def get_fonts_overrides():
-    """Get font overrides"""
-    try:
-        # This would integrate with the actual font system
-        # For now, return empty overrides
-        overrides = {}
-        return jsonify({'status': 'success', 'data': {'overrides': overrides}})
-    except Exception as e:
-        logger.error('Unhandled exception', exc_info=True)
-        return jsonify({'status': 'error', 'message': 'An error occurred; see logs for details', 'details': describe_exception(e)}), 500
-
-@api_v3.route('/fonts/overrides', methods=['POST'])
-def save_fonts_overrides():
-    """Save font overrides"""
-    try:
-        data = request.get_json(silent=True)
-        if not data:
-            return jsonify({'status': 'error', 'message': 'No data provided'}), 400
-
-        # This would integrate with the actual font system
-        return jsonify({'status': 'success', 'message': 'Font overrides saved'})
-    except Exception as e:
-        logger.error('Unhandled exception', exc_info=True)
-        return jsonify({'status': 'error', 'message': 'An error occurred; see logs for details', 'details': describe_exception(e)}), 500
-
-@api_v3.route('/fonts/overrides/<element_key>', methods=['DELETE'])
-def delete_font_override(element_key):
-    """Delete font override"""
-    try:
-        # This would integrate with the actual font system
-        return jsonify({'status': 'success', 'message': f'Font override for {element_key} deleted'})
-    except Exception as e:
-        logger.error('Unhandled exception', exc_info=True)
-        return jsonify({'status': 'error', 'message': 'An error occurred; see logs for details', 'details': describe_exception(e)}), 500
-
 @api_v3.route('/fonts/upload', methods=['POST'])
 def upload_font():
     """Upload font file"""