#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/outbound_job.go

@@ -0,0 +1,51 @@
+package entity
+
+import (
+	"errors"
+	"time"
+)
+
+// OutboundJob is a delivery unit with retry state (PLAN.md section 3 and 6.3).
+type OutboundJob struct {
+	attempt     int
+	maxAttempts int
+}
+
+var ErrOutboundJobMaxAttemptsExceeded = errors.New("outbound job: attempt count would exceed max_attempts")
+
+func NewOutboundJob(maxAttempts int) *OutboundJob {
+	return &OutboundJob{maxAttempts: maxAttempts}
+}
+
+func (j *OutboundJob) Attempt() int { return j.attempt }
+
+// RecordAttempt enforces "attempt <= max_attempts" (PLAN.md section 3).
+func (j *OutboundJob) RecordAttempt() error {
+	if j.attempt >= j.maxAttempts {
+		return ErrOutboundJobMaxAttemptsExceeded
+	}
+	j.attempt++
+	return nil
+}
+
+// retrySchedule mirrors the accumulated-wait table in PLAN.md section 6.3.
+var retrySchedule = []time.Duration{
+	0,
+	5 * time.Minute,
+	15 * time.Minute,
+	1 * time.Hour,
+	2 * time.Hour,
+	4 * time.Hour,
+	8 * time.Hour,
+	12 * time.Hour,
+}
+
+// NextBackoff returns the wait before the next attempt, per the schedule in section 6.3.
+// Attempts beyond the table repeat the last (12h) step, matching the "9+: every 12h" rule.
+func (j *OutboundJob) NextBackoff() time.Duration {
+	idx := j.attempt
+	if idx >= len(retrySchedule) {
+		idx = len(retrySchedule) - 1
+	}
+	return retrySchedule[idx]
+}