feat: notification cooldown dedup for events and problems (notif-31)

Store last notify time by dedup_key/fingerprint, gate dispatch before
channels; config SAC_NOTIFY_*_COOLDOWN_SEC, migration 008.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/services/notify_dispatch.py

@@ -1,18 +1,19 @@
 """Dispatch ingest notifications per global policy (severity → channels)."""
 
+import logging
+
 from sqlalchemy.orm import Session
 
 from app.models import Event, Problem
 from app.services import email_notify, telegram_notify, webhook_notify
+from app.services.notification_cooldown import should_notify_event, should_notify_problem
 from app.services.notification_policy import get_effective_notification_policy
 from app.services.notification_severity import severity_meets_minimum
-from app.services.notification_settings import CHANNEL_EMAIL, CHANNEL_TELEGRAM, CHANNEL_WEBHOOK
+
+logger = logging.getLogger(__name__)
 
 
-def notify_event(event: Event, *, db: Session | None = None) -> None:
-    policy = get_effective_notification_policy(db)
-    if not severity_meets_minimum(event.severity, policy.min_severity):
-        return
+def _dispatch_event_channels(event: Event, *, db: Session | None, policy) -> None:
     if policy.use_telegram:
         telegram_notify.notify_event(event, db=db, apply_policy_gate=False)
     if policy.use_webhook:
@@ -21,13 +22,28 @@ def notify_event(event: Event, *, db: Session | None = None) -> None:
         email_notify.notify_event(event, db=db, apply_policy_gate=False)
 
 
-def notify_problem(problem: Problem, event: Event | None = None, *, db: Session | None = None) -> None:
-    policy = get_effective_notification_policy(db)
-    if not severity_meets_minimum(problem.severity, policy.min_severity):
-        return
+def _dispatch_problem_channels(problem: Problem, event: Event | None, *, db: Session | None, policy) -> None:
     if policy.use_telegram:
         telegram_notify.notify_problem(problem, event, db=db, apply_policy_gate=False)
     if policy.use_webhook:
         webhook_notify.notify_problem(problem, event, db=db, apply_policy_gate=False)
     if policy.use_email:
         email_notify.notify_problem(problem, event, db=db, apply_policy_gate=False)
+
+
+def notify_event(event: Event, *, db: Session | None = None) -> None:
+    policy = get_effective_notification_policy(db)
+    if not severity_meets_minimum(event.severity, policy.min_severity):
+        return
+    if not should_notify_event(event, db):
+        return
+    _dispatch_event_channels(event, db=db, policy=policy)
+
+
+def notify_problem(problem: Problem, event: Event | None = None, *, db: Session | None = None) -> None:
+    policy = get_effective_notification_policy(db)
+    if not severity_meets_minimum(problem.severity, policy.min_severity):
+        return
+    if not should_notify_problem(problem, db):
+        return
+    _dispatch_problem_channels(problem, event, db=db, policy=policy)