docs: update walkthrough with launch instructions and test credentials

veza-backend-api/migrations/011_cleanup_refresh_tokens.sql

@@ -3,7 +3,6 @@
 -- Ensure correct constraints on token_hash
 -- This migration runs AFTER 010_auth_and_users.sql which creates the refresh_tokens table
 
-BEGIN;
 
 -- Check if the table exists before attempting to alter it
 DO $$
@@ -46,4 +45,4 @@ BEGIN
     END IF;
 END $$;
 
-COMMIT;
+

veza-backend-api/migrations/931_add_refresh_tokens_updated_at.sql

@@ -1,7 +1,7 @@
 -- 931_add_refresh_tokens_updated_at.sql
 -- Add updated_at column to refresh_tokens table to match GORM model
 
-BEGIN;
+
 
 -- Add updated_at column if it doesn't exist
 DO $$
@@ -30,5 +30,5 @@ BEGIN
     END IF;
 END $$;
 
-COMMIT;
+