db: regenerate integration.creator_id migrations for all dialects

The PR only shipped a SQLite creator_id migration; MySQL and PostgreSQL were
missing (CodeRabbit) and the SQLite one lacked ON DELETE SET NULL. Regenerate
on top of dev's widget_secret base:

- sqlite 0041: ADD creator_id ... REFERENCES user(id) ON DELETE SET NULL
- mysql 0043: ADD creator_id + FK ON DELETE set null (hand-written snapshot
  from dev's 0042 to avoid touching the pre-existing custom_widget_secret FK
  that must stay under MySQL's 64-char identifier limit)
- postgresql 0009: ADD creator_id + FK ON DELETE set null

Schema already declares onDelete: set null on integration.creatorId.

packages/db/migrations/sqlite/0041_add_integration_creator_id.sql

@@ -0,0 +1 @@
+ALTER TABLE `integration` ADD `creator_id` text REFERENCES user(id) ON DELETE SET NULL;

packages/db/migrations/sqlite/meta/_journal.json

@@ -288,6 +288,13 @@
       "when": 1783176100870,
       "tag": "0040_add_widget_secret",
       "breakpoints": true
+    },
+    {
+      "idx": 41,
+      "version": "6",
+      "when": 1783786326756,
+      "tag": "0041_add_integration_creator_id",
+      "breakpoints": true
     }
   ]
 }