release: 0.1.0: Phases 0-11: panel, Postfix/DKIM, milter, backup, Docker image

Initial feature-complete implementation of the v1.0 specification (phases 0-11 of `docs/implementation-plan.md`).
Added:
  - Panel (Go, single static binary) with SQLite persistence, one-time
  - Domain management with per-domain DKIM (RSA-2048, generated in pure Go) and
  - Application (sender identity) management: SASL credentials via `sasldb2`,
  - Full Postfix relay config generated from env at container start: SMTPS 465,
  - Journal milter (pure Go, `go-milter`) recording every send to `send_log`;
  … (6 more in CHANGELOG)

Full detail: CHANGELOG.md (0.1.0).

test/e2e/wait.go

@@ -0,0 +1,29 @@
+package e2e
+
+import (
+	"fmt"
+	"time"
+)
+
+// waitFor polls check every interval until it returns true or timeout elapses.
+// Every wait in this suite goes through here — no fixed sleeps standing in for
+// a readiness check (plan C.4): a passing check ends the wait immediately, and
+// a timeout fails with what was being waited for, not a bare "timed out".
+func waitFor(what string, timeout, interval time.Duration, check func() (bool, error)) error {
+	deadline := time.Now().Add(timeout)
+	var lastErr error
+	for {
+		ok, err := check()
+		if ok {
+			return nil
+		}
+		lastErr = err
+		if time.Now().After(deadline) {
+			if lastErr != nil {
+				return fmt.Errorf("timed out after %s waiting for %s: %w", timeout, what, lastErr)
+			}
+			return fmt.Errorf("timed out after %s waiting for %s", timeout, what)
+		}
+		time.Sleep(interval)
+	}
+}