perf: implement virtualization and search debouncing for EntityBrowser (#121)

* refactor: simplify panel.ts to minimal web component

- Remove unused panel and route setters
- Compact code formatting while maintaining readability
- Keep shadow DOM for CSS isolation (required for Home Assistant)
- Maintain CSS loading for both shadow DOM and document head (for portals)

* perf: implement virtualization for EntityBrowser to fix performance with large entity lists

- Add @tanstack/react-virtual for list virtualization
- Implement virtual scrolling in EntitiesBrowserTab component
- Add React.memo to EntityItem components
- Create performance test route at /test/performance
- Flatten data structure for efficient rendering
- Expected 70-90% performance improvement with 1500+ entities

* perf: add search debouncing and fix virtual list item heights

- Implement 300ms debounce for search input to reduce recalculations
- Fix overlapping virtual list items by increasing heights:
  - Entity items: 60px → 72px with proper padding
  - Headers: 40px → 48px with fixed height
- Add proper spacing between entity cards (mb-2)
- Increase card padding from p-2 to p-3 for better touch targets
- Add tmp/ to .gitignore to exclude temporary files

* fix: update EntityBrowser tests for virtualization

- Mock @tanstack/react-virtual to render all items in tests
- Update test expectations to work with virtualized list
- Add dynamic virtualizer mock that calculates items based on count
- Adjust search test for debounced input
- Format files with Prettier

* style: fix prettier formatting in EntityBrowser test

* fix: resolve TypeScript errors in EntityBrowser test

- Remove unused mockVirtualItems variable
- Add proper types to virtualizer mock function parameters
- Fix ESLint no-explicit-any errors

* fix: add explicit type for items array in virtualizer mock

Author: fx

.gitignore

@@ -51,4 +51,7 @@ lerna-debug.log*
 .env.sentry-build-plugin
 
 # Claude settings
-.claude/settings.local.json
+.claude/settings.local.json
+
+# Temporary files
+tmp/

package-lock.json

@@ -31,6 +31,7 @@
     "@tanstack/react-router-devtools": "^1.122.0",
     "@tanstack/react-start": "^1.122.1",
     "@tanstack/react-store": "^0.7.1",
+    "@tanstack/react-virtual": "^3.13.12",
     "@types/js-yaml": "^4.0.9",
     "home-assistant-js-websocket": "^9.5.0",
     "js-yaml": "^4.1.0",