When the backend was down the cabinet got stuck on a blank loader: the bootstrap
token refresh used bare axios with no timeout (hung forever), and every
interceptor guard required an HTTP response — so a transport-level failure had
zero handling and no error UI ever appeared.
Add a full-screen ServiceUnavailableScreen (extends the existing blocking-store
pattern) shown whenever the backend is unreachable, that auto-recovers when it
returns:
- New 'backend_unavailable' blocking type + BlockingOverlay branch; mirrors
MaintenanceScreen, CloudWarningIcon, i18n in ru/en/zh/fa.
- api/health.ts: pingBackend() probes the root /health/unified (bypasses the
/api baseURL + interceptor); URL derived from the origin for remote/sub-path
deploys; 502/503/504 count as down. reportPossibleBackendDown() confirms an
outage with a liveness probe before flipping, so a one-off blip never blanks a
loaded app.
- Detected from the response interceptor (no-response) and the bootstrap refresh
path; doRefresh gets a timeout so it can no longer hang.
- A transport failure during refresh now PRESERVES the session (distinguished
from a rejected token via lastFailureWasTransport) instead of logging the user
out, so recovery actually resumes.
- Recovery lifts the overlay + refetches for an already-loaded session, and only
hard-reloads when the initial bootstrap never reached the backend — no lost
form state. Manual retry + 5s auto-poll. Dev proxy for /health.
Pairs with backend feat(deleted-users) — when the cabinet returns
403 {detail: {code: 'account_deleted', message, bot_username,
telegram_deep_link}} the SPA shows a dedicated screen instead of the
generic auth-error toast.
* Adds AccountDeletedScreen with localized title/description, an
Open-bot button using the backend-provided telegram_deep_link, and a
Retry button that clears the block + reloads (so the next request
observes the now-revived row).
* useBlockingStore gains accountDeleted slice mirroring the existing
maintenance/channel-subscription/blacklisted slots — consistent with
the precedent for cross-cutting 403 codes.
* apiClient: AccountDeletedError type + isAccountDeletedError guard +
response interceptor routes the 403 into the blocking store.
* i18n: ru/en/zh/fa parity for title, description, openBot, retry, hint.
No behavior change for ACTIVE users. BLOCKED users still get the
generic 403 (the backend keeps the message opaque for admin actions).
- Channel subscription blocking screen with per-channel status display
- Safe URL handling with protocol validation (no open redirect)
- Race-condition-safe subscription check with useRef guard
- Admin channel management page with create, toggle, delete
- Error handlers on all admin mutations with haptic feedback
- Proper type guard for channel subscription error detection
- Accessibility: aria-labels on icon-only buttons
- Localization: en, ru, zh, fa translations
