feat: Telegram notifications from SAC on ingest

Send Telegram alerts for high/critical events and new Problems.
Configurable via TELEGRAM_* env vars; ingest never fails on send errors.

backend/app/api/v1/events.py

@@ -15,6 +15,7 @@ from app.schemas.list_models import EventDetail, EventListResponse, EventSummary
 from app.services.ingest import ingest_event
 from app.services.problems import maybe_create_problem
 from app.services.schema_validate import validate_event_payload
+from app.services.telegram_notify import notify_event, notify_problem
 
 router = APIRouter(prefix="/events", tags=["events"])
 
@@ -39,8 +40,12 @@ def post_event(
 
     event, created = ingest_event(db, payload)
     problem = None
+    problem_created = False
     if created:
-        problem = maybe_create_problem(db, event)
+        problem, problem_created = maybe_create_problem(db, event)
+        notify_event(event)
+        if problem is not None and problem_created:
+            notify_problem(problem, event)
     db.commit()
 
     settings = get_settings()