feat(electron): error handling foundation

Adds the infrastructure for a coherent client-side error story:

- `lib/errors.ts`: canonical ApiError + QuotaExceededError, `toUserMessage`
  (friendly strings for ApiError/ZodError/network errors, strips Electron
  IPC message prefixes), `logError` (expected), `reportError` (unexpected).
- `lib/query-client.ts`: QueryClient factory with sane retry defaults (no
  retry on 4xx except 408/429, 2 retries otherwise; 0 mutation retries),
  `QueryCache` onError logs + opts in via `meta.toastOnError`, and
  `MutationCache` onError toasts `toUserMessage(err)` by default with
  `meta.suppressToast` as the opt-out.
- `components/app-error-boundary.tsx` + `error-fallback.tsx`: two boundaries
  (top-level outside the router, route-level inside) with a Card-based
  fallback offering 'Go home' + 'Try again'. Route boundary resets on
  pathname change and clears React Query error cache on retry.
- `main/ipc-utils.ts` + main.ts migration: `safeHandle` wraps ipcMain.handle
  so main-process failures log with full stack and surface a sanitized
  message to the renderer. `link:fetch-metadata` keeps its null contract
  but now logs.
- `useCreateParticle` opts out of the global toast (compose-overlay renders
  its own quota UX) so nothing double-toasts.

Render crashes now have a recovery UI, every mutation gets a free error
toast, and silent-catch cleanup + Sentry land in follow-up PRs.

js/package.json

@@ -65,6 +65,7 @@
     "radix-ui": "^1.4.3",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
+    "react-error-boundary": "^6.1.1",
     "react-markdown": "^10.1.0",
     "react-router-dom": "^7.13.0",
     "react-use": "^17.6.0",