fix(db): wait for/retry DB DNS resolution before drizzle-kit migrate (GRO-2163)

A fresh migrate-schema pod occasionally hits a transient CoreDNS miss
(EAI_AGAIN) on groombook-postgres-rw.<ns>.svc on its first attempt.
With backoffLimit: 2 the retry pod usually wins, but three unlucky
attempts in a row trips BackoffLimitExceeded and the Job is recreated
on every Flux reconcile (3+ Completed events observed in 8 min in uat).

Add packages/db/scripts/wait-for-db.mjs: a tiny no-deps Node 22 script
that parses DATABASE_URL, resolves the hostname via node:dns.promises
with exponential backoff (12 attempts, ~30s total) and only exits 0
once a real IP is returned. EAI_AGAIN / ENOTFOUND / EAI_NODATA are
retried; any other DNS error is surfaced so drizzle-kit gets a clear
message instead of being starved by retries.

Wire it as a pnpm `pre-migrate` (and `pre-seed` / `pre-reset`) hook
in @groombook/db so pnpm auto-runs it before any of the data-plane
commands. Mirrors the belt-and-braces pattern used in GRO-1985
(disable Corepack download fallback): do not try to outsmart CoreDNS,
just do not ask drizzle-kit to perform the very first DNS lookup of a
freshly-scheduled pod.

Defaults are env-tunable (WAIT_FOR_DB_MAX_ATTEMPTS, _BASE_DELAY_MS,
_MAX_DELAY_MS, _SKIP) so a future uat-debug pod can sidestep the
wait if needed.

Refs: GRO-2163, GRO-1985.

packages/db/package.json

@@ -18,7 +18,10 @@
   "scripts": {
     "build": "tsc --project .",
     "generate": "drizzle-kit generate",
+    "pre-migrate": "node ./scripts/wait-for-db.mjs",
     "migrate": "drizzle-kit migrate",
+    "pre-seed": "node ./scripts/wait-for-db.mjs",
+    "pre-reset": "node ./scripts/wait-for-db.mjs",
     "seed": "tsx src/seed.ts",
     "reset": "tsx src/reset.ts && drizzle-kit migrate && tsx src/seed.ts",
     "studio": "drizzle-kit studio",