fix(scheduling): extend AnonymizeStaleGuestAccounts with additional field scrubbing

AnonymizeStaleGuestAccounts now additionally scrubs profile_pic_url (NULL), referral_code (NULL), notes (NULL), and data_retention_consent (FALSE) for stale guest accounts. Previously only scrubbed name, email, phone, and date_of_birth. Ensures comprehensive PII removal for guests with no active/pending bookings and last booking over 6 months old.

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

@@ -374,6 +374,10 @@ func AnonymizeStaleGuestAccounts(ctx context.Context) error {
 		email = 'anon-' || id || '@anon.invalid',
 		phone = '000000000000',
 		date_of_birth = '1900-01-01',
+		profile_pic_url = NULL,
+		referral_code = NULL,
+		notes = NULL,
+		data_retention_consent = FALSE,
 		updated_at = NOW()
 		WHERE account_role = 'guest'
 		  AND id NOT IN (