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).

internal/postfix/queue.go

@@ -0,0 +1,22 @@
+package postfix
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+// Queue returns Postfix's own human-readable mail-queue listing (spec 7.2.11):
+// active, deferred and held messages, exactly as an administrator would see
+// via the CLI. The command takes a single fixed flag and no user input, so it
+// never goes through a shell (spec 7.6.3). The panel is responsible for
+// escaping the output before display (spec 7.6.7); this function returns it
+// as-is.
+func Queue() (string, error) {
+	cmd := exec.Command("postqueue", "-p")
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return "", fmt.Errorf("postqueue -p: %w: %s", err, strings.TrimSpace(string(out)))
+	}
+	return string(out), nil
+}