fix: address PR review findings

Fix (10 of 15 findings):

plugin-repos/march-madness/requirements.txt:
  Add urllib3>=1.26.0 — manager.py directly imports from urllib3; it was
  an undeclared transitive dependency via requests.

scripts/dev/dev_plugin_setup.sh:
  Restore subshell form (cd "$target_dir" && git pull --rebase) || true
  so the shell's working directory is not permanently changed after the
  if-cd block. Previous fix for SC2015 leaked cwd into the remainder of
  the script.

src/base_classes/sports.py:
  Narrow 'except Exception' to 'except RuntimeError as e' and log via
  self.logger.debug — Path.home() raises only RuntimeError for service
  users; other exceptions should not be silently swallowed.

src/config_service.py:
  Fix stale "MD5 checksum" in ConfigVersion.__init__ docstring (line 40);
  the implementation uses SHA-256 since the Codacy fix.

src/wifi_manager.py:
  Log the last-resort AP enable failure with exc_info=True instead of
  silently passing — failure here means the device may be unreachable.

web_interface/blueprints/pages_v3.py:
  Log the outer metadata pre-load exception at debug level instead of
  swallowing it silently; schema still loads fully below.

src/background_data_service.py:
  Remove unused 'timeout' parameter from shutdown() — executor.shutdown()
  does not accept timeout; update __del__ caller accordingly.

src/font_manager.py:
  Validate URL scheme before urlretrieve — reject non-http/https schemes
  (e.g. file://) to prevent reading local files from config-supplied URLs.

src/plugin_system/plugin_executor.py:
  Simplify redundant except tuple: (PluginTimeoutError, PluginError,
  Exception) → Exception, which already covers the others.

test/test_display_controller.py:
  Mark empty test_plugin_discovery_and_loading as @pytest.mark.skip with
  reason. Move duplicate 'from datetime import datetime' to module header
  and remove the stray mid-module copy.

Skip (5 of 15 findings, with reasons):
  - pytest 9.0.3 concerns: full suite already verified (467 pass, 18 pre-existing)
  - Pillow 12.2.0 API concerns: no deprecated APIs in codebase; tests + Pi smoke test pass
  - diagnose_web_ui.sh sudo validation: set -e already ensures fail-fast on any sudo failure
  - app.py request-logging except: must stay silent (recursive logging risk); annotated
  - app.py SSE file-read except: genuinely transient I/O; annotated

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

web_interface/blueprints/pages_v3.py

@@ -395,8 +395,8 @@ def _load_plugin_config_partial(plugin_id):
                                             config['images'] = config.get('images', []) + new_images
                             except Exception as e:
                                 print(f"Warning: Could not load metadata for {plugin_id}: {e}")
-            except Exception:  # nosec B110 - metadata pre-load is optional; schema loads fully below
-                pass  # Will load schema properly below
+            except Exception as e:  # nosec B110 - metadata pre-load is optional; schema loads fully below
+                logger.debug("Metadata pre-load skipped for plugin %s: %s", plugin_id, e)
         
         # Get plugin schema
         schema = {}