feat(web): plugin install auto-enables + persistent restart nudge

Getting a plugin onto the display used to take three disconnected manual
steps: install from the store, flip its enable toggle, then restart the
display service - with no in-UI hint that steps 2 and 3 were needed (only
docs/GETTING_STARTED.md mentions it).

- installPlugin() now enables the plugin immediately on successful install
  (owner-confirmed behavior change: always auto-enable, no opt-out; users
  who don't want it running toggle it off as before), then shows a
  persistent toast ("... restart the display to show it") with an inline
  "Restart Now" button wired to the existing restartDisplay() - the same
  function the three existing Restart Display buttons call.
- notification.js: show() accepts optional { actionLabel, onAction } to
  render one inline action button per toast. Callbacks are stored per
  notification id and cleaned up on dismiss; a new triggerAction() public
  method runs the callback and dismisses. The global showNotification()
  shorthand now forwards a full options object as its second argument
  (legacy type-string calls unchanged).

Scope note: applies to the plugin store's install path (window.installPlugin).
The custom-registry install path keeps its existing behavior.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KEZK1P1Q1fu5pcuVrkrCFZ

web_interface/static/v3/plugins_manager.js

@@ -3888,6 +3888,19 @@ window.installPlugin = function(pluginId, branch = null) {
     .then(data => {
         showNotification(data.message, data.status);
         if (data.status === 'success') {
+            // Enable immediately so install -> enable is one step, then nudge
+            // for the display restart that's needed before it shows on the
+            // matrix (persistent toast; duration 0 = stays until dismissed).
+            window.togglePlugin(pluginId, true);
+            showNotification(
+                `${pluginId} installed and enabled — restart the display to show it`,
+                {
+                    type: 'success',
+                    duration: 0,
+                    actionLabel: 'Restart Now',
+                    onAction: () => restartDisplay()
+                }
+            );
             // Refresh installed plugins list, then re-render store to update badges
             loadInstalledPlugins();
             setTimeout(() => applyStoreFiltersAndSort(true), 500);