feat: production-readiness hardening across security, async, DB, ops

Security
- SSRF: async DNS resolver; allow_redirects=False on all outbound clients;
  matrix homeserver_url validated on create/update/test; update_provider
  and email_bot merge incoming config and reject ***-masked secrets.
- Auth: bcrypt offloaded to asyncio.to_thread; JWT now carries iss/aud +
  leeway and rejects missing claims; setup TOCTOU closed inside a
  transaction; rate limits extended (default 600/min, 10/min on password
  change, 30/min on needs-setup); constant-time login to prevent username
  enumeration.
- Config: rejects known dev secret keys; validates CORS origin schemes,
  port range, token lifetimes.
- Webhook handlers stream-read body with a 1 MiB cap; Discord 429 retries
  bounded (3 attempts, Retry-After capped at 60 s).
- CSP + HSTS added to SecurityHeadersMiddleware.

Async / runtime
- SQLite engine: WAL, synchronous=NORMAL, foreign_keys=ON, busy_timeout,
  pool_pre_ping, dispose on shutdown.
- Lifespan shutdown now stops scheduler before closing HTTP session and
  disposing the engine.
- Shared aiohttp session locked against concurrent first-caller races;
  core NotificationDispatcher accepts and reuses it.
- Storage and scheduled backup writes wrapped in asyncio.to_thread.
- NUT client writes bounded by asyncio.wait_for.
- Telegram poller switched from 3 s short-poll to 30 s interval + 25 s
  long-poll (~10x fewer API calls).

Database
- New performance-indexes migration covers every FK/owner column and
  hot-path composite (notification_tracker(provider_id, enabled);
  event_log(user_id, created_at DESC); webhook_payload_log(provider_id,
  created_at DESC); action_execution(action_id, started_at DESC)).
- New schema_version table for future upgrade gating.
- __system__ placeholder user (id=0) seeded so user_id=0 system defaults
  satisfy the newly enforced FK; filtered out of /auth/needs-setup,
  /api/users, and setup.
- list_notification_trackers rewritten to batched loads (was 1+N+N*M).
- Retention job extended to event_log, webhook_payload_log, and
  action_execution; retention days exposed as a setting.

Scheduler
- AsyncIOScheduler job_defaults: coalesce, misfire_grace_time=300,
  max_instances=1.

Ops
- uvicorn runs with proxy_headers, forwarded_allow_ips,
  timeout_graceful_shutdown; access log suppressed in non-debug.
- FastAPI version string now reads from importlib.metadata.
- New /api/ready endpoint separate from /api/health.
- docker-compose drops the ALLOW_PRIVATE_URLS=1 default, adds mem/cpu/pid
  limits, read_only + tmpfs, cap_drop:ALL, no-new-privileges; healthcheck
  targets /api/ready.
- CI now runs on push/PR with backend pytest, frontend svelte-check +
  build, and a non-push image build; release workflow gated on tests,
  publishes immutable sha-<commit> image tag, adds Trivy scan.

Tests
- New packages/server/tests/ with 29 passing tests: config validation,
  JWT round-trip + aud/alg=none rejection, SSRF scheme and private-range
  enforcement (sync + async), Discord bounded retry, and a lifespan-level
  /api/health + /api/ready smoke check.
- Renamed the misnamed services/test_dispatch.py to manual_dispatch.py so
  pytest never auto-collects production code.

Frontend
- /login now redirects already-authenticated users to /, shows a distinct
  'backend unreachable' banner (en/ru) when /auth/needs-setup fails.

packages/server/src/notify_bridge_server/services/telegram_poller.py

@@ -127,7 +127,14 @@ async def stop_bot_if_unused(bot_id: int) -> None:
 
 
 def schedule_bot_polling(bot_id: int) -> None:
-    """Add a polling job for a bot (idempotent)."""
+    """Add a polling job for a bot (idempotent).
+
+    We schedule at a 30 s interval, but each tick calls ``getUpdates`` with
+    ``timeout=25`` — Telegram holds the connection open until either an
+    update arrives or the timeout elapses, so in practice the bot streams
+    updates with sub-second latency while consuming ~2 API calls / minute
+    per bot (down from 20 under the old 3 s short-poll).
+    """
     scheduler = get_scheduler()
     job_id = f"telegram_poll_{bot_id}"
     if scheduler.get_job(job_id):
@@ -135,13 +142,13 @@ def schedule_bot_polling(bot_id: int) -> None:
     scheduler.add_job(
         _poll_bot,
         "interval",
-        seconds=3,
+        seconds=30,
         id=job_id,
         args=[bot_id],
         replace_existing=True,
         max_instances=1,
     )
-    _LOGGER.info("Started polling for bot %d", bot_id)
+    _LOGGER.info("Started polling for bot %d (long-poll, 25s timeout)", bot_id)
 
 
 def unschedule_bot_polling(bot_id: int) -> None:
@@ -233,8 +240,10 @@ async def _poll_bot(bot_id: int) -> None:
         from .http_session import get_http_session
         http = await get_http_session()
         client = TelegramClient(http, bot_token)
+        # Long-poll: hold connection open until an update arrives or 25 s
+        # elapse. Drastically cuts API calls vs. 3 s short-poll.
         result = await client.get_updates(
-            offset=offset + 1 if offset else None, limit=50,
+            offset=offset + 1 if offset else None, limit=50, timeout=25,
         )
         if not result.get("success"):
             err_text = str(result.get("error") or "")