#1: implement F0 foundation - monorepo, migrations, Go domain layer, service skeletons, CI

Stands up the LambdaMail monorepo per PLAN.md's F0 milestone: local dev
scaffolding (.env.example, Makefile, .gitignore excluding PLAN.md/docs/
.superpowers/), the full initial Postgres schema as a golang-migrate
migration, the complete Go domain layer for services/protocols (value
objects, entities, domain events - zero external imports beyond
github.com/google/uuid) with unit tests, health-checked service skeletons
for auth/storage (TypeScript) and webmail (Next.js), a local
docker-compose.yaml wiring all services together, a language-enforcement
lint script, and a GitHub Actions CI workflow.

Built via 11 sequential tasks under subagent-driven development, each with
an independent implementer + reviewer cycle. Fixes applied during review:
DomainName.IsPunycode() added to satisfy the promised interface; ioredis
default-import typing under NodeNext; next.js bumped 15.0.3->15.5.21 to
resolve high/critical CVEs; lang-lint.mjs corrected to not flag its own
banned-terms list; web service healthcheck added so compose --wait
actually waits on it; webmail Dockerfile's missing public/ directory:
protocols go.mod version aligned with CI's Go 1.22 pin.

Known follow-ups for later phases (not blocking F0): go-arch-lint isn't
wired into CI yet; live docker compose up and migration apply have not
been exercised in this dev environment (no Docker/psql available here)
and will get their first real run in CI, which does have Docker.

services/protocols/internal/domain/entity/tls_policy.go

@@ -0,0 +1,25 @@
+package entity
+
+// TLSPolicy is the effective transport security policy for an outbound destination
+// (PLAN.md section 3: DANE has precedence over MTA-STS, RFC 8461 section 2).
+type TLSPolicy struct {
+	daneAvailable   bool
+	mtaSTSAvailable bool
+}
+
+func NewTLSPolicy(daneAvailable, mtaSTSAvailable bool) TLSPolicy {
+	return TLSPolicy{daneAvailable: daneAvailable, mtaSTSAvailable: mtaSTSAvailable}
+}
+
+// Effective returns "dane", "mta-sts" or "opportunistic" following the precedence
+// rule in PLAN.md section 5 / RFC 8461 section 2.
+func (p TLSPolicy) Effective() string {
+	switch {
+	case p.daneAvailable:
+		return "dane"
+	case p.mtaSTSAvailable:
+		return "mta-sts"
+	default:
+		return "opportunistic"
+	}
+}