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 ✓

dist/services/apiProxy.js

@@ -70,8 +70,11 @@ class ApiProxy {
         console.log(`[ApiProxy] Starting built-in Node.js translation proxy on port ${this.port}`);
         // Use Electron's Node.js binary to run our translation proxy
         const proxyScript = path.join(__dirname, 'translationProxy.js');
-        const nodeBin = process.execPath;
-        this.proxyProcess = child_process.spawn(nodeBin, ['--no-sandbox', proxyScript], {
+        // Use system node (not Electron's process.execPath which starts a GUI)
+        const nodeBin = process.execPath.includes('electron') || process.execPath.includes('AG-X')
+            ? child_process.execSync('which node 2>/dev/null || echo /usr/bin/node').toString().trim()
+            : process.execPath;
+        this.proxyProcess = child_process.spawn(nodeBin, [proxyScript], {
             stdio: ['ignore', 'pipe', 'pipe'],
             detached: false,
             env: { ...process.env },