fix: reorder uuid_generate_v7 migration to run before tables that use it

- Rename 021_create_uuid_v7_function.sql to 009_create_uuid_v7_function.sql
- Add CREATE EXTENSION IF NOT EXISTS pgcrypto for gen_random_bytes()
- Remove obsolete 022_migrate_to_uuid_v7.sql (already handled by table def)

This fixes the error where migration 017 tried to use uuid_generate_v7()
before it was created.

backend/migrations/009_create_uuid_v7_function.sql

@@ -3,6 +3,9 @@
 -- UUID v7 format: tttttttt-tttt-7xxx-yxxx-xxxxxxxxxxxx
 -- Where: t = timestamp, 7 = version, y = variant, x = random
 
+-- Enable pgcrypto extension for gen_random_bytes()
+CREATE EXTENSION IF NOT EXISTS pgcrypto;
+
 -- Create or replace the uuid_generate_v7 function
 CREATE OR REPLACE FUNCTION uuid_generate_v7()
 RETURNS uuid AS $$

backend/migrations/022_migrate_to_uuid_v7.sql

@@ -1,20 +0,0 @@
--- Migration: Update UUID tables to use UUID v7
--- Description: Updates default values for notifications, tickets, job_payments to use uuid_generate_v7()
--- Requires: 021_create_uuid_v7_function.sql (must run first)
-
--- Update notifications table to use UUID v7
-ALTER TABLE notifications ALTER COLUMN id SET DEFAULT uuid_generate_v7();
-
--- Update tickets table to use UUID v7
-ALTER TABLE tickets ALTER COLUMN id SET DEFAULT uuid_generate_v7();
-
--- Update ticket_messages table to use UUID v7
-ALTER TABLE ticket_messages ALTER COLUMN id SET DEFAULT uuid_generate_v7();
-
--- Update job_payments table to use UUID v7
-ALTER TABLE job_payments ALTER COLUMN id SET DEFAULT uuid_generate_v7();
-
--- Comments
-COMMENT ON TABLE notifications IS 'User notifications (UUID v7 IDs)';
-COMMENT ON TABLE tickets IS 'Support tickets (UUID v7 IDs)';
-COMMENT ON TABLE job_payments IS 'Payment records for job postings (UUID v7 IDs)';