fix(testing): wire dbChainMock.db to shared transaction and execute fns

dbChainMock.db.transaction was an inline vi.fn() separate from the exported
dbChainMockFns.transaction, so dbChainMockFns.transaction.mockResolvedValueOnce
and assertions silently targeted the wrong instance. dbChainMock.db also
omitted execute, so tests for any module that calls db.execute (logging-session,
table service, billing balance) would throw TypeError. Both mocks now reference
the module-level constants so overrides and resetDbChainMock affect the same fn.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: waleedlatif1

packages/testing/src/mocks/database.mock.ts

@@ -192,7 +192,8 @@ export const dbChainMock = {
     insert,
     update,
     delete: del,
-    transaction: vi.fn(async (cb: (tx: typeof dbChainMock.db) => unknown) => cb(dbChainMock.db)),
+    execute,
+    transaction,
   },
 }