#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/folder.go

@@ -0,0 +1,24 @@
+package entity
+
+import "github.com/google/uuid"
+
+// Folder is an IMAP folder entity. uidNext is strictly monotonic (RFC 3501 section 2.3.1.1),
+// enforced per PLAN.md section 3.
+type Folder struct {
+	mailboxID uuid.UUID
+	name      string
+	uidNext   int64
+}
+
+func NewFolder(mailboxID uuid.UUID, name string) *Folder {
+	return &Folder{mailboxID: mailboxID, name: name, uidNext: 1}
+}
+
+func (f *Folder) Name() string { return f.name }
+
+// NextUID allocates and returns the next UID, then advances the counter.
+func (f *Folder) NextUID() int64 {
+	uid := f.uidNext
+	f.uidNext++
+	return uid
+}