Delete access tokens on user delete (#34036)

Trying to delete a user record from our admin panel throws the following
error:

`update or delete on table "users" violates foreign key constraint
"access_tokens_user_id_fkey" on table "access_tokens"
Detail: Key (id)=(....) is still referenced from table "access_tokens".`

We need to add a cascade delete to the `access_tokens` table.

Release Notes:

- N/A

crates/collab/migrations/20250707182700_add_access_tokens_cascade_delete_on_user.sql

@@ -0,0 +1,3 @@
+ALTER TABLE access_tokens DROP CONSTRAINT access_tokens_user_id_fkey;
+ALTER TABLE access_tokens ADD CONSTRAINT access_tokens_user_id_fkey
+    FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;