#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_test.go

@@ -0,0 +1,40 @@
+package entity
+
+import "testing"
+
+func TestOutboundJob_RecordAttempt_AllowsUpToMax(t *testing.T) {
+	j := NewOutboundJob(3)
+	for i := 0; i < 3; i++ {
+		if err := j.RecordAttempt(); err != nil {
+			t.Fatalf("attempt %d: unexpected error: %v", i+1, err)
+		}
+	}
+	if j.Attempt() != 3 {
+		t.Errorf("Attempt() = %d, want 3", j.Attempt())
+	}
+}
+
+func TestOutboundJob_RecordAttempt_RejectsBeyondMax(t *testing.T) {
+	j := NewOutboundJob(1)
+	if err := j.RecordAttempt(); err != nil {
+		t.Fatalf("unexpected error on first attempt: %v", err)
+	}
+	if err := j.RecordAttempt(); err == nil {
+		t.Fatal("expected error: attempt must never exceed max_attempts (PLAN.md section 3), got nil")
+	}
+}
+
+func TestOutboundJob_NextBackoff_IsMonotonicPerRetryTable(t *testing.T) {
+	// Backoff schedule from PLAN.md section 6.3: attempts 1-4 map to
+	// immediate, +5m, +15m, +1h.
+	j := NewOutboundJob(8)
+	var prev int64 = -1
+	for i := 0; i < 4; i++ {
+		j.RecordAttempt()
+		d := j.NextBackoff()
+		if int64(d) < prev {
+			t.Errorf("attempt %d: backoff %v is not >= previous backoff", i+1, d)
+		}
+		prev = int64(d)
+	}
+}