refactor(db): port metrics storage + service domains to sqlc (#75)

First tranche of the ~300-site raw SQL port. Metrics: node/service/
instance rows via generated queries; aggregation moved off TimescaleDB's
time_bucket onto portable date_bin (PG14+); interval uptime returns epoch
seconds; per-container writes dropped (container_metrics FKs a different
model — collector shape never matched). Domains: all reads/writes through
sqlcdb including the create transaction via WithTx; default-domain and
services.domain invariants unchanged. Both paths covered by live
Postgres tests gated on METRICS_TEST_DSN.

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ROADMAP2.md

@@ -537,7 +537,7 @@ and wired refs, one click or one CLI call.
   workspace, CLI `environments` + MCP parity. Per-env vars/domains ride the
   service's own scope (one env per service); promote ships via preview
   promote.
-- [ ] **sqlc port** — ~140 raw `database/sql` sites → `sqlc/queries/`.
+- [ ] **sqlc port** — ~300 raw `database/sql` sites → `sqlc/queries/`. Done in tranches (dynamic queries stay raw): metrics storage + service domains ported.
 - [ ] **Tests** — canvas/wizard frontend coverage, deployment/template/
   webhook table tests, Playwright e2e golden path.
 - [x] **First-run wizard** — public `GET /setup/status` + authed