feat: global notification policy severity to channels (notif-22)

Singleton notification_policy table, NOTIFY_MIN_SEVERITY/CHANNELS env,
central dispatch gate, Settings policy UI, migration 007.

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

backend/app/services/notification_policy.py

@@ -0,0 +1,130 @@
+"""Global notification policy: severity ≥ min → selected channels."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
+from app.config import get_settings
+from app.models.notification_channel import NotificationChannel
+from app.models.notification_policy import POLICY_ROW_ID, NotificationPolicy
+from app.services.notification_settings import (
+    CHANNEL_EMAIL,
+    CHANNEL_TELEGRAM,
+    CHANNEL_WEBHOOK,
+    VALID_SEVERITIES,
+)
+
+DEFAULT_CHANNELS = frozenset({CHANNEL_TELEGRAM, CHANNEL_WEBHOOK, CHANNEL_EMAIL})
+
+
+@dataclass(frozen=True)
+class NotificationPolicyConfig:
+    min_severity: str
+    use_telegram: bool
+    use_webhook: bool
+    use_email: bool
+    source: str  # env | db
+
+    def allows_channel(self, channel: str) -> bool:
+        if channel == CHANNEL_TELEGRAM:
+            return self.use_telegram
+        if channel == CHANNEL_WEBHOOK:
+            return self.use_webhook
+        if channel == CHANNEL_EMAIL:
+            return self.use_email
+        return False
+
+
+def _parse_channels_csv(value: str) -> tuple[bool, bool, bool]:
+    parts = {p.strip().lower() for p in value.split(",") if p.strip()}
+    return (
+        CHANNEL_TELEGRAM in parts or "tg" in parts,
+        CHANNEL_WEBHOOK in parts,
+        CHANNEL_EMAIL in parts or "mail" in parts or "smtp" in parts,
+    )
+
+
+def _policy_from_env() -> NotificationPolicyConfig:
+    settings = get_settings()
+    use_tg, use_wh, use_em = _parse_channels_csv(settings.notify_channels)
+    min_sev = settings.notify_min_severity.strip() or "warning"
+    if min_sev not in VALID_SEVERITIES:
+        min_sev = "warning"
+    return NotificationPolicyConfig(
+        min_severity=min_sev,
+        use_telegram=use_tg,
+        use_webhook=use_wh,
+        use_email=use_em,
+        source="env",
+    )
+
+
+def get_effective_notification_policy(db: Session | None = None) -> NotificationPolicyConfig:
+    if db is None:
+        from app.database import SessionLocal
+
+        session = SessionLocal()
+        try:
+            return get_effective_notification_policy(session)
+        finally:
+            session.close()
+
+    row = db.get(NotificationPolicy, POLICY_ROW_ID)
+    env_cfg = _policy_from_env()
+    if row is None:
+        return env_cfg
+
+    min_sev = (row.min_severity or "").strip() or env_cfg.min_severity
+    if min_sev not in VALID_SEVERITIES:
+        min_sev = env_cfg.min_severity
+
+    return NotificationPolicyConfig(
+        min_severity=min_sev,
+        use_telegram=bool(row.use_telegram),
+        use_webhook=bool(row.use_webhook),
+        use_email=bool(row.use_email),
+        source="db",
+    )
+
+
+def _sync_channel_min_severity(db: Session, min_severity: str) -> None:
+    for channel in (CHANNEL_TELEGRAM, CHANNEL_WEBHOOK, CHANNEL_EMAIL):
+        row = db.get(NotificationChannel, channel)
+        if row is not None:
+            row.min_severity = min_severity
+
+
+def upsert_notification_policy(
+    db: Session,
+    *,
+    min_severity: str,
+    use_telegram: bool,
+    use_webhook: bool,
+    use_email: bool,
+) -> NotificationPolicyConfig:
+    if min_severity not in VALID_SEVERITIES:
+        raise ValueError(f"invalid min_severity: {min_severity}")
+
+    row = db.get(NotificationPolicy, POLICY_ROW_ID)
+    if row is None:
+        row = NotificationPolicy(
+            id=POLICY_ROW_ID,
+            min_severity=min_severity,
+            use_telegram=use_telegram,
+            use_webhook=use_webhook,
+            use_email=use_email,
+        )
+        db.add(row)
+    else:
+        row.min_severity = min_severity
+        row.use_telegram = use_telegram
+        row.use_webhook = use_webhook
+        row.use_email = use_email
+
+    _sync_channel_min_severity(db, min_severity)
+    db.commit()
+    db.refresh(row)
+    return get_effective_notification_policy(db)