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/services/problems.py

@@ -16,9 +16,9 @@ PROBLEM_TYPES = frozenset(
 HIGH_SEVERITIES = frozenset({"high", "critical"})
 
 
-def maybe_create_problem(db: Session, event: Event) -> Problem | None:
+def maybe_create_problem(db: Session, event: Event) -> tuple[Problem | None, bool]:
     if event.severity not in HIGH_SEVERITIES and event.type not in PROBLEM_TYPES:
-        return None
+        return None, False
 
     rule_id = "high_severity" if event.severity in HIGH_SEVERITIES else f"type:{event.type}"
 
@@ -34,7 +34,7 @@ def maybe_create_problem(db: Session, event: Event) -> Problem | None:
         .limit(1)
     )
     if existing:
-        return existing
+        return existing, False
 
     # dedupe: one open problem per host+rule (append event link)
     open_problem = db.scalar(
@@ -51,7 +51,7 @@ def maybe_create_problem(db: Session, event: Event) -> Problem | None:
         db.add(ProblemEvent(problem_id=open_problem.id, event_id=event.id))
         open_problem.updated_at = event.received_at
         db.flush()
-        return open_problem
+        return open_problem, False
 
     problem = Problem(
         host_id=event.host_id,
@@ -65,4 +65,4 @@ def maybe_create_problem(db: Session, event: Event) -> Problem | None:
     db.flush()
     db.add(ProblemEvent(problem_id=problem.id, event_id=event.id))
     db.flush()
-    return problem
+    return problem, True