Integrate JailJS for CSP-restricted execution in browser extension

Major changes:
- Migrate browser-extension to use web-ui package (85% code reduction)
- Add JailJS content script with ES6+ transform support
- Expose DOM constructors (Event, KeyboardEvent, etc.) to JailJS
- Support top-level await by wrapping code in async IIFE
- Add returnFile() support in JailJS execution
- Refactor KeyStore into pluggable storage-adapter pattern
- Make ChatPanel configurable with sandboxUrlProvider and additionalTools
- Update jailjs to 0.1.1

Files deleted (33 duplicate files):
- All browser-extension components, dialogs, state, tools, utils
- Now using web-ui versions via @mariozechner/pi-web-ui

Files added:
- packages/browser-extension/src/content.ts (JailJS content script)
- packages/web-ui/src/state/storage-adapter.ts
- packages/web-ui/src/state/key-store.ts

Browser extension now has only 5 source files (down from 38).

packages/browser-extension/manifest.firefox.json

@@ -24,6 +24,14 @@
     "open_at_install": false
   },
   "content_security_policy": "script-src 'self' 'wasm-unsafe-eval' https://cdn.jsdelivr.net https://cdnjs.cloudflare.com https://unpkg.com https://cdn.skypack.dev; object-src 'self'",
+  "content_scripts": [
+    {
+      "matches": ["https://*/*", "http://localhost/*", "http://127.0.0.1/*"],
+      "js": ["content.js"],
+      "run_at": "document_idle",
+      "all_frames": false
+    }
+  ],
   "permissions": [
     "storage",
     "activeTab",