chore: remove dead code, deprecate unused plugin APIs (over-engineering audit) (#783)

* chore: remove dead code, deprecate unused plugin APIs (over-engineering audit)

Whole-tree audit. Every symbol was checked against core, the plugin
monorepo and all eight third-party plugins in plugins.json first.

- Deprecate (removal 3.10.0) plugin-facing methods nothing calls:
  LogoDownloader bulk download, ConfigManager backup/secret wrappers,
  APIHelper extras, BackgroundDataService poll API, PluginManager /
  PluginStateManager info readers, and a few CacheManager, FontManager,
  BaseOddsManager, DynamicTeamResolver methods and PluginTestCase.
  plugin_api_usage.py learns their receiver names; DEPRECATIONS doc
  regenerated.
- Remove core-internal dead code: CacheMetrics, Vegas status/stats
  plumbing, sync "new cycle" message (followers ignore unknown types),
  unused operation types, test-only PluginCatalog readers, IPC to_dict
  and ping, _parse_form_value, CacheStrategyProtocol, ErrorAggregator
  callbacks, duplicate web response helpers.
- Web UI: drop never-mounted json-file-manager.js, the example widget,
  utils/error_handler.js, four uncalled PluginAPI methods, and 29
  escapeHtml shims (call window.LEDEscape directly). Public globals,
  BaseWidget and widget names unchanged.
- Remove six one-off scripts (owner decision) and the unused markupsafe
  and pytest-mock pins.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(web): calendar picker error text goes in a text node, not innerHTML

Same output as the escaped innerHTML it replaces; clears Codacy's
XSS-pattern alerts on the line.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

src/cache_manager.py

@@ -35,13 +35,13 @@ import tempfile
 from src.cache.memory_cache import MemoryCache, default_max_size
 from src.cache.disk_cache import DiskCache
 from src.cache.cache_strategy import CacheStrategy
-from src.cache.cache_metrics import CacheMetrics
 from src.logging_config import get_logger
 
 # Canonical implementation lives in src.cache.disk_cache; re-exported here
 # because this module's docstring documents it and external code may import
 # it from either path.
 from src.cache.disk_cache import DateTimeEncoder  # noqa: F401 - deliberate re-export
+from src.deprecation import deprecated
 
 # CacheManager.config_manager not built yet (None means "not available").
 _UNSET: Any = object()
@@ -149,10 +149,7 @@ class CacheManager:
             max_size=default_max_size(), cleanup_interval=300.0
         )
         self._disk_cache_component = DiskCache(cache_dir=self.cache_dir, logger=self.logger)
-        # No config manager: CacheStrategy keeps the parameter for callers but
-        # reads nothing from it, and passing ours would build it eagerly.
-        self._strategy_component = CacheStrategy(logger=self.logger)
-        self._metrics_component = CacheMetrics(logger=self.logger)
+        self._strategy_component = CacheStrategy()
         
         # Disk cleanup configuration
         self._disk_cleanup_interval_hours = 24  # Run cleanup every 24 hours
@@ -398,6 +395,7 @@ class CacheManager:
         # caller gets as is.
         self._disk_cache_component.set(key, data)
 
+    @deprecated("3.10.0", "use get(key, max_age=3600)")
     def load_cache(self, key: str) -> Optional[Dict[str, Any]]:
         """Load data from cache with memory caching."""
         # Check memory cache first (1 minute TTL)
@@ -607,13 +605,6 @@ class CacheManager:
             duration = time.time() - start_time
             space_freed_mb = stats['space_freed_bytes'] / (1024 * 1024)
             
-            # Record metrics
-            self._metrics_component.record_disk_cleanup(
-                files_cleaned=stats['files_deleted'],
-                space_freed_mb=space_freed_mb,
-                duration_sec=duration
-            )
-            
             # Log summary
             if stats['files_deleted'] > 0:
                 self.logger.info(
@@ -796,6 +787,7 @@ class CacheManager:
         data_type = self.get_data_type_from_key(key)
         return self.get_cached_data_with_strategy(key, data_type)
 
+    @deprecated("3.10.0")
     def generate_sport_cache_key(self, sport: str, date_str: Optional[str] = None) -> str:
         """
         Centralized cache key generation for sports data.