v2.0.5: Fix E2E flow - proxy, welcome screen, provider sync

Critical fixes:
- Translation proxy now uses system Node.js (not Electron binary)
- Removed duplicate proxy start causing port conflicts
- Added port availability check before spawning proxy
- Fixed welcome:choice double resolve()
- Fixed settings.html close using deprecated remote
- Fixed translationProxy /v1 for openai-compat backends
- Proxy no longer detached/unref - properly tracked as child
- SingletonLock cleanup on startup

Verified E2E:
- Welcome screen on first run ✓
- Provider selection works ✓
- Settings save + sync ✓
- Translation proxy starts correctly ✓
- LS connects to proxy ✓
- --ag-reset works ✓

package.json

@@ -1,7 +1,7 @@
 {
   "name": "ag-x",
   "productName": "AG X",
-  "version": "2.0.4",
+  "version": "2.0.5",
   "description": "AG X - Agentic Desktop Application",
   "homepage": "https://ag-x.dev",
   "author": {