fix: Provider sync on every startup + sandbox fixes (v2.0.4)

Critical fixes:
- ALWAYS sync active AG X provider to endpoints.json on startup
  (previously only synced on first run, causing LS to use stale data)
- Add --no-sandbox to proxy process spawns (fixes SIGTRAP crash on Linux)
- Add --no-sandbox for all Electron modes (not just headless)
- Add --ag-reset flag to re-trigger welcome screen
- Bump version to 2.0.4

Root causes fixed:
1. endpoints.json was never updated after first-run, so LS used wrong provider
2. Electron child processes (translation proxy) crashed due to SUID sandbox
3. No way to re-show provider selection after initial setup

dist/services/apiProxy.js

@@ -71,7 +71,7 @@ class ApiProxy {
         // 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, [proxyScript], {
+        this.proxyProcess = child_process.spawn(nodeBin, ['--no-sandbox', proxyScript], {
             stdio: ['ignore', 'pipe', 'pipe'],
             detached: false,
             env: { ...process.env },