fix(setup): ensure step 69 runs without issues (#11503)

## Which problems are solved

https://github.com/zitadel/zitadel/pull/11484 introduced a regression
that causes the setup process to fail on existing Zitadel deployments.
This prevents users from upgrading to recent versions without
encountering setup failures.

## How the problems are solved

Setup step 69 has been corrected to properly handle existing deployment
configurations and prevent setup failures during initialization and
upgrades.

## Additional Context

introduced by
[7a41fe968b](https://github.com/zitadel/zitadel/commit/7a41fe968b9fcb69b378336740b74e5448c1ff81)

### Testing

- [x] Verified setup succeeds on fresh deployments
- [x] Verified setup succeeds on existing deployments
- [x] Verified migration from PostgreSQL 17 to 18 after running setup of
this version

cmd/setup/69.sql

@@ -1,13 +1,31 @@
 DO
 $do$
 BEGIN
+   -- Convert objects to logged first (if unlogged)
    IF EXISTS (SELECT 1 FROM pg_class WHERE oid = 'cache.objects'::REGCLASS AND relpersistence = 'u') THEN
         ALTER TABLE IF EXISTS cache.objects
             SET LOGGED;
    END IF;
-   IF EXISTS (SELECT 1 FROM pg_class WHERE oid = 'cache.string_keys'::REGCLASS AND relpersistence = 'u') THEN
+
+   -- Convert string_keys to logged (if unlogged)
+   -- Drop the FK constraint first to allow converting cache.string_keys (and avoid loggedness-change restrictions involving the FK)
+   IF EXISTS (SELECT 1 FROM pg_class WHERE oid = to_regclass('cache.objects') AND relpersistence = 'u') THEN
+        ALTER TABLE IF EXISTS cache.objects
+            SET LOGGED;
+   END IF;
+
+   -- Convert string_keys to logged (if unlogged)
+   -- Drop the FK constraint first to avoid conflict with parent table conversion
+   IF EXISTS (SELECT 1 FROM pg_class WHERE oid = to_regclass('cache.string_keys') AND relpersistence = 'u') THEN
+        ALTER TABLE IF EXISTS cache.string_keys
+            DROP CONSTRAINT IF EXISTS fk_object;
         ALTER TABLE IF EXISTS cache.string_keys
             SET LOGGED;
+        ALTER TABLE IF EXISTS cache.string_keys
+            ADD CONSTRAINT fk_object
+            FOREIGN KEY(cache_name, object_id)
+            REFERENCES cache.objects(cache_name, id)
+            ON DELETE CASCADE;
    END IF;
 
    CREATE UNLOGGED TABLE IF NOT EXISTS cache.objects_default