Fix cross-compartment crashes, add per-container vector settings

- Replace Intl.DateTimeFormat and RTCPeerConnection constructor overrides
  with safe non-constructor approaches to fix Discord and other complex apps
- Add per-container vector toggles (gear icon in popup)
- Add per-container delete button in popup
- Fix Reset All not removing orphaned containers
- Popup now only shows managed containers
- Bump version to 0.5.3

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 2,
   "name": "ContainSite",
-  "version": "0.5.2",
+  "version": "0.5.3",
   "description": "Per-container fingerprint isolation — each container gets its own device identity",
   "permissions": [
     "contextualIdentities",