feat(admin): surface configuration problems in the admin panel

Add GET /api/admin/health powered by a config health service that
detects common deployment mistakes: missing or read-only data volume,
broken tariffs/locale-override/guides JSON files, payment providers
enabled without credentials, webhook providers without
WEBHOOK_BASE_URL, no enabled payment methods, missing or non-https
mini app URL, missing Redis, partially configured SMTP, untrusted
reverse proxy, invalid bot token, missing/mismatched/failing Telegram
webhook and unreachable Remnawave panel. Network checks (Telegram,
panel) are cached for two minutes; ?refresh=1 forces a re-check.

The admin UI shows the alerts as a banner on the dashboard with
per-section navigation chips and a manual re-check button, and as a
filtered banner inside each affected section. Alerts are localized
via admin_health_* keys with built-in Russian fallbacks.

backend/bot/app/web/admin_api.py

@@ -9,6 +9,7 @@ from bot.app.web.admin_api_impl import (
     backups as _backups,
     broadcast as _broadcast,
     common as _common,
+    health as _health,
     logs as _logs,
     panel as _panel,
     payments as _payments,
@@ -28,6 +29,7 @@ _MODULES = (
     _runtime,
     _auth,
     _common,
+    _health,
     _stats,
     _users,
     _payments,

backend/bot/app/web/admin_api_impl/health.py

@@ -0,0 +1,19 @@
+# ruff: noqa: F401,F403,F405,I001
+from datetime import datetime, timezone
+
+from ._runtime import *  # noqa: F403,F405
+from .auth import _require_admin_user_id
+from .common import _ok
+from bot.services.config_health_service import collect_config_alerts
+
+
+async def admin_health_route(request: web.Request) -> web.Response:
+    _require_admin_user_id(request)
+    refresh = str(request.query.get("refresh", "")).strip().lower() in {"1", "true", "yes"}
+    alerts = await collect_config_alerts(request, refresh=refresh)
+    return _ok(
+        {
+            "alerts": alerts,
+            "checked_at": datetime.now(timezone.utc).isoformat(),
+        }
+    )

backend/bot/app/web/admin_api_impl/routes.py

@@ -6,6 +6,7 @@ def setup_admin_routes(app: web.Application) -> None:
     router = app.router
     router.add_get("/api/admin/me", admin_me_route)
     router.add_get("/api/admin/stats", admin_stats_route)
+    router.add_get("/api/admin/health", admin_health_route)
 
     router.add_get("/api/admin/users", admin_users_list_route)
     router.add_get("/api/admin/users/{user_id:-?\\d+}", admin_user_detail_route)