Hub: add POST /api/v1/notify endpoint for customer notifications

- New notification relay endpoint: receives events from customer controllers,
  looks up customer email preferences, sends via Resend HTTP API
- New tables: customer_notifications (per-customer email + event prefs),
  notification_log (audit trail for all notification attempts)
- Hungarian email template with severity, event type, timestamp
- Config: notifications.resend_api_key + notifications.from_email
- Test events always pass event-type filter

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hub/internal/store/store.go

@@ -69,10 +69,88 @@ func (s *Store) migrate() error {
 
 		CREATE INDEX IF NOT EXISTS idx_reports_customer
 			ON reports(customer_id, received_at DESC);
+
+		CREATE TABLE IF NOT EXISTS customer_notifications (
+			customer_id TEXT PRIMARY KEY,
+			email TEXT NOT NULL DEFAULT '',
+			enabled_events TEXT NOT NULL DEFAULT '[]',
+			created_at DATETIME DEFAULT (datetime('now')),
+			updated_at DATETIME DEFAULT (datetime('now'))
+		);
+
+		CREATE TABLE IF NOT EXISTS notification_log (
+			id INTEGER PRIMARY KEY AUTOINCREMENT,
+			customer_id TEXT NOT NULL,
+			event_type TEXT NOT NULL,
+			severity TEXT NOT NULL,
+			message TEXT NOT NULL,
+			status TEXT NOT NULL DEFAULT 'pending',
+			error_message TEXT,
+			created_at DATETIME DEFAULT (datetime('now'))
+		);
+
+		CREATE INDEX IF NOT EXISTS idx_notification_log_customer
+			ON notification_log(customer_id, created_at DESC);
 	`)
 	return err
 }
 
+// NotificationPrefs holds per-customer notification preferences.
+type NotificationPrefs struct {
+	CustomerID    string
+	Email         string
+	EnabledEvents []string
+}
+
+// GetNotificationPrefs returns notification preferences for a customer.
+func (s *Store) GetNotificationPrefs(customerID string) (*NotificationPrefs, error) {
+	var email, eventsJSON string
+	err := s.db.QueryRow(
+		"SELECT email, enabled_events FROM customer_notifications WHERE customer_id = ?",
+		customerID,
+	).Scan(&email, &eventsJSON)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil
+		}
+		return nil, err
+	}
+
+	var events []string
+	json.Unmarshal([]byte(eventsJSON), &events)
+
+	return &NotificationPrefs{
+		CustomerID:    customerID,
+		Email:         email,
+		EnabledEvents: events,
+	}, nil
+}
+
+// SaveNotificationPrefs creates or updates notification preferences for a customer.
+func (s *Store) SaveNotificationPrefs(customerID, email string, enabledEvents []string) error {
+	eventsJSON, _ := json.Marshal(enabledEvents)
+	_, err := s.db.Exec(`
+		INSERT INTO customer_notifications (customer_id, email, enabled_events, updated_at)
+		VALUES (?, ?, ?, datetime('now'))
+		ON CONFLICT(customer_id) DO UPDATE SET
+			email = excluded.email,
+			enabled_events = excluded.enabled_events,
+			updated_at = datetime('now')`,
+		customerID, email, string(eventsJSON),
+	)
+	return err
+}
+
+// LogNotification records a notification attempt.
+func (s *Store) LogNotification(customerID, eventType, severity, message, status, errorMsg string) error {
+	_, err := s.db.Exec(`
+		INSERT INTO notification_log (customer_id, event_type, severity, message, status, error_message)
+		VALUES (?, ?, ?, ?, ?, ?)`,
+		customerID, eventType, severity, message, status, errorMsg,
+	)
+	return err
+}
+
 // SaveReport stores a new report. The reportJSON should be the raw JSON payload.
 func (s *Store) SaveReport(customerID string, reportJSON []byte) error {
 	// Parse denormalized fields from the JSON