fix: migration 040 — run UPDATE before ADD CONSTRAINT (correct order)

ALTER TABLE ADD CONSTRAINT validates existing rows immediately, so the
UPDATE must run first to migrate 'standard' → 'bronze' before the new
constraint is applied.

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

backend/migrations/040_fixes.sql

@@ -15,15 +15,15 @@ CREATE UNIQUE INDEX IF NOT EXISTS uq_chat_rooms_general_per_hotel
   WHERE type = 'general';
 
 -- Fix 2: replace 'standard' tier with 'bronze' (the UI uses bronze/silver/gold/platinum)
--- Drop the old check constraint that only allows 'standard' instead of 'bronze'
+-- Drop the old check constraint first
 ALTER TABLE guests DROP CONSTRAINT IF EXISTS guests_loyalty_tier_check;
 
--- Add the correct constraint
-ALTER TABLE guests
-  ADD CONSTRAINT guests_loyalty_tier_check
-  CHECK (loyalty_tier IN ('bronze', 'silver', 'gold', 'platinum'));
-
--- Migrate existing 'standard' rows to 'bronze'
+-- Migrate existing 'standard' rows to 'bronze' (must happen BEFORE adding the new constraint)
 UPDATE guests
 SET loyalty_tier = 'bronze'
 WHERE loyalty_tier NOT IN ('bronze', 'silver', 'gold', 'platinum');
+
+-- Now add the correct constraint
+ALTER TABLE guests
+  ADD CONSTRAINT guests_loyalty_tier_check
+  CHECK (loyalty_tier IN ('bronze', 'silver', 'gold', 'platinum'));