general cleanup - removed old comments, enforced naming conventions etc

backend/infra/migrations/001_add_user_id.sql

@@ -0,0 +1,16 @@
+
+ALTER TABLE addresses 
+ADD COLUMN user_id VARCHAR(128);
+
+UPDATE addresses 
+SET user_id = 'legacy_user' 
+WHERE user_id IS NULL;
+
+ALTER TABLE addresses 
+ALTER COLUMN user_id SET NOT NULL;
+
+CREATE INDEX idx_addresses_user_id ON addresses(user_id);
+
+ALTER TABLE addresses DROP CONSTRAINT IF EXISTS addresses_address_key;
+
+ALTER TABLE addresses ADD CONSTRAINT addresses_user_address_unique UNIQUE (user_id, address);