test(db): resolve the integration DSN at run time instead of storing an IP (#161)

setup-test-db.sh wrote .env.test once with the Postgres container's bridge IP
baked in, and Docker reassigns those on recreation. The file rotted silently:
its stored 172.22.0.18 belongs to **gitea** as of today, and an earlier drift
had the suite pointing its TRUNCATE at **postgres-pantry** — which it would
have wiped had the credentials happened to match.

Root-cause fix: stop persisting a host at all.

- scripts/resolve-test-db.sh re-derives the DSN from the live container and
  rewrites .env.test. Resolution order is TEST_DATABASE_URL, then the
  container's published host port, then the bridge IP. `docker port
  postgres-personal` reports 127.0.0.1:5432 since the 2026-08-17 PG17
  migration, so loopback is what gets used here — and a loopback address
  cannot be reassigned to another container, which is the whole point.
  (Note this supersedes the smarthome CLAUDE.md's "postgres-personal publishes
  no host port"; that is now stale.) The bridge-IP fallback is kept for a host
  where the port is not published, and the script never prints the password.
- Wired as `pretest:integration`, so npm runs it before every integration run.
  .env.test becomes a generated artifact rather than stored configuration.
- setup-test-db.sh now only creates the database and copies the schema, then
  delegates to the resolver.
- helpers.ts::assertTestDatabase stays and its message now points at the
  resolver rather than at `docker inspect`. It still earns its place: running
  vitest directly bypasses the pretest hook, and a stale .env.test would then
  still be read.

Docs: CLAUDE.md gains a Testing section carrying this, the prisma-generate
trap for a fresh checkout or worktree, and the frozen-clock rule for tests
whose subject is defined relative to "now". AGENTS.md updated for the same, and
for lint now being blocking.

package.json

@@ -10,6 +10,7 @@
     "test": "vitest run --config vitest.config.ts",
     "test:watch": "vitest --config vitest.config.ts",
     "test:setup": "bash scripts/setup-test-db.sh",
+    "pretest:integration": "bash scripts/resolve-test-db.sh",
     "test:integration": "vitest run --config vitest.integration.config.ts",
     "test:all": "npm test && npm run test:integration"
   },