Replace nested Promise.all([insert, update]) + outer
Promise.all([withBrand, cookies()]) with sequential awaits in
verifyWaterPin, mirroring the admin-portal pattern from commit
ca79896 and src/lib/water-admin-pin-auth.ts.
Symptom: field PIN works once, fails after logout until reset.
Root cause is the same family flagged in ca79896: cookies()
corrupts Next.js's request-scoped AsyncLocalStorage when called
from inside a pg transaction, and nested Promise.all inside
the transaction makes the failure non-deterministic.
Also adds scripts/diag-water-pin.mjs for one-shot prod DB
inspection if the symptom persists post-deploy.
Tyler