fix(web): widget cache-busting, dead frontend code, and dependency pins (#656)

- Plugin-supplied widgets load as /static/plugin-widgets/...js?v=<plugin
  version>, so an update isn't hidden behind the year-long immutable cache.
- Fire-and-forget loadInstalledPlugins() calls catch the rejection it has
  already reported, so the global handler no longer adds a second toast.
- Timezone picker renders again when the General partial is re-injected.
- Remove dead code: executePluginAction's six plugin-id fallbacks and
  [DEBUG] logging, window.currentPluginConfig and every read of it, the
  file-upload JSON delete branch, unused PluginAPI / PluginInstallManager /
  PluginStateManager helpers, loadPluginWidgetsFromManifest, the stale
  install_manager.js and LEDVisibility fallbacks, error_handler.js's global
  escapeHtml, 13 unused CSS rules, and stale comments/no-op returns.
- pytz < 2027, psutil < 7 in requirements-test.txt, pytest-cov < 8.
- Pin anthropics/claude-code-action to the commit v1 resolves to.

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

web_interface/templates/v3/partials/plugin_config.html

@@ -1101,6 +1101,7 @@
                 (function() {
                     var WIDGET = {{ str_widget|tojson|safe }};
                     var PLUGIN = {{ plugin_id|tojson|safe }};
+                    var VERSION = {{ ((plugin.version if plugin is defined and plugin else '') or '')|string|tojson|safe }};
                     function initPluginWidget() {
                         if (!window.LEDMatrixWidgets || !window.LEDMatrixWidgets.ensureWidget) {
                             setTimeout(initPluginWidget, 50);
@@ -1109,7 +1110,7 @@
                         var container = document.getElementById('{{ field_id }}_container');
                         var fallback = document.getElementById('{{ field_id }}');
                         if (!container) { return; }
-                        window.LEDMatrixWidgets.ensureWidget(WIDGET, PLUGIN).then(function(available) {
+                        window.LEDMatrixWidgets.ensureWidget(WIDGET, PLUGIN, VERSION).then(function(available) {
                             if (!available) { container.remove(); return; }
                             var widget = window.LEDMatrixWidgets.get(WIDGET);
                             if (!widget || typeof widget.render !== 'function') { container.remove(); return; }