#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/valueobject/domain_name.go

@@ -0,0 +1,49 @@
+package valueobject
+
+import (
+	"errors"
+	"strings"
+)
+
+// DomainName is an RFC 1035 fully-qualified domain name, normalized to lowercase.
+type DomainName struct {
+	value string
+}
+
+var (
+	ErrDomainNameEmpty         = errors.New("domain name: must not be empty")
+	ErrDomainNameNotFQDN       = errors.New("domain name: must contain at least one dot (not a FQDN)")
+	ErrDomainNameInvalidLabel  = errors.New("domain name: label must not start or end with a hyphen")
+)
+
+// NewDomainName validates and normalizes raw into a DomainName.
+func NewDomainName(raw string) (DomainName, error) {
+	if raw == "" {
+		return DomainName{}, ErrDomainNameEmpty
+	}
+	lower := strings.ToLower(raw)
+	labels := strings.Split(lower, ".")
+	if len(labels) < 2 {
+		return DomainName{}, ErrDomainNameNotFQDN
+	}
+	for _, label := range labels {
+		if label == "" || strings.HasPrefix(label, "-") || strings.HasSuffix(label, "-") {
+			return DomainName{}, ErrDomainNameInvalidLabel
+		}
+	}
+	return DomainName{value: lower}, nil
+}
+
+func (d DomainName) String() string { return d.value }
+
+// IsPunycode reports whether the domain name is IDNA/punycode-encoded.
+// It returns true if any label of the domain starts with the ASCII Compatible Encoding prefix "xn--".
+func (d DomainName) IsPunycode() bool {
+	labels := strings.Split(d.value, ".")
+	for _, label := range labels {
+		if strings.HasPrefix(label, "xn--") {
+			return true
+		}
+	}
+	return false
+}