feat: dual TTL reservation cleanup and guest account anonymization

CleanupOldReservations now handles four reservation types:
logged-in (1hr), anonymous (10min), admin-walkin (10min), admin-callin (1hr).

AnonymizeStaleGuestAccounts scrubs PII from guest accounts whose last booking
was 6+ months ago and who have no pending/confirmed bookings. Financial records
remain intact — only personal data is wiped (UK GDPR compliance).
Triggered on every GetAvailableHours call.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/handlers/scheduling/time-blockers.go

@@ -336,6 +336,8 @@ func CheckTimeBlockerOverlap(ctx context.Context, startTime, endTime time.Time)
 // CleanupOldReservations deletes expired reservations:
 // - Logged-in (RESERVATION:user): older than 1 hour
 // - Anonymous (RESERVATION:anon): older than 10 minutes
+// - Admin walk-in (RESERVATION:admin:walkin:%): older than 10 minutes
+// - Admin call-in (RESERVATION:admin:callin:%): older than 1 hour
 func CleanupOldReservations(ctx context.Context) error {
 	oneHourAgo := time.Now().Add(-1 * time.Hour)
 	tenMinutesAgo := time.Now().Add(-10 * time.Minute)
@@ -344,6 +346,36 @@ func CleanupOldReservations(ctx context.Context) error {
 		DELETE FROM time_blockers
 		WHERE (description LIKE 'RESERVATION:user:%' AND created_at < $1)
 		   OR (description LIKE 'RESERVATION:anon:%' AND created_at < $2)
-	`, oneHourAgo, tenMinutesAgo)
+		   OR (description LIKE 'RESERVATION:admin:walkin:%' AND created_at < $2)
+		   OR (description LIKE 'RESERVATION:admin:callin:%' AND created_at < $3)
+	`, oneHourAgo, tenMinutesAgo, oneHourAgo)
+	return err
+}
+
+// AnonymizeStaleGuestAccounts anonymizes personal data for guest accounts
+// whose last booking was more than 6 months ago (UK GDPR storage limitation).
+// Financial records (bookings, payments) remain intact — only PII is scrubbed.
+// Active/pending bookings are excluded so the salon can still contact the guest.
+func AnonymizeStaleGuestAccounts(ctx context.Context) error {
+	_, err := db.DB.Exec(ctx, `
+		UPDATE users SET
+			n_first_name = 'Guest',
+			n_last_name = 'Anonymized',
+			email = 'anon-' || id || '@anon.invalid',
+			phone = '000000000000',
+			date_of_birth = '1900-01-01',
+			updated_at = NOW()
+		WHERE account_role = 'guest'
+		  AND id NOT IN (
+			  SELECT user_id FROM bookings WHERE status IN ('pending', 'confirmed')
+		  )
+		  AND id IN (
+			  SELECT user_id
+			  FROM bookings
+			  WHERE user_id IS NOT NULL
+			  GROUP BY user_id
+			  HAVING MAX(start_time) < NOW() - INTERVAL '6 months'
+		  )
+	`)
 	return err
 }