fix: remove unused local variable assignments (pyflakes F841)

Dead assignments removed across src/ and web_interface/:

- background_data_service: drop future= on fire-and-forget executor.submit
- base_classes/baseball: drop font= (all rendering uses self.fonts['time'])
- base_classes/hockey: drop status_short= (never referenced after assignment)
- common/cli: drop game_helper=/config_helper= bindings in import-test block;
  constructors called for instantiation-only validation
- common/display_helper: drop text_width= (x_position uses display_width
  directly); drop draw= in create_error_image (uses _draw_centered_text)
- config_manager: remove dead secrets_content loading block in migration path
  (comment already noted save_config_atomic handles secrets internally)
- display_manager: drop setup_start= (timing was never completed or read)
- font_manager: drop target_path= (catalog uses font_file_path directly);
  drop face=/font= bindings in validate_font (validation by construction —
  TypeError on failure is the signal, not the return value)
- font_test_manager: drop width=/height= (draw_text uses display_manager directly)
- plugin_system/state_reconciliation: drop manager= (only config/disk/state_mgr used)
- plugin_system/store_manager: drop result= on pip install subprocess.run
  (check=True raises on failure; stdout unused)
- web_interface/blueprints/pages_v3: drop main_config_path=""/secrets_config_path=""
  (render_template uses config_manager.get_*_path() inline)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/font_manager.py

@@ -697,8 +697,6 @@ class FontManager:
             fonts_dir = Path("assets/fonts")
             ensure_directory_permissions(fonts_dir, get_assets_dir_mode())
 
-            target_path = os.path.join(fonts_dir, f"{family_name}.{font_file_path.rsplit('.', 1)[-1]}")
-
             # Add to catalog
             self.font_catalog[family_name] = font_file_path
             self.clear_cache()
@@ -744,11 +742,11 @@ class FontManager:
 
             if font_path.endswith('.bdf'):
                 # Try to load BDF font
-                face = freetype.Face(font_path)
+                freetype.Face(font_path)
                 return {"valid": True, "type": "bdf", "family": "unknown"}
             elif font_path.endswith('.ttf'):
                 # Try to load TTF font
-                font = ImageFont.truetype(font_path, 12)
+                ImageFont.truetype(font_path, 12)
                 return {"valid": True, "type": "ttf", "family": "unknown"}
             else:
                 return {"valid": False, "error": "Unsupported font format"}