v0.88.0: app-email SMTP relay (in-process shim + per-app injection)

In-process go-smtp shim (Shape 1): apps → shim → hub → Resend, Resend key stays
hub-side. From-header allowlist (reject 5xx pre-hub), single-shot raw-MIME forward,
status→SMTP mapping. Global + per-app toggles gate compose-time env injection from
.felhom.yml smtp_mapping. Hungarian UI on settings + app config pages.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

controller/internal/mailrelay/lifecycle.go

@@ -0,0 +1,79 @@
+package mailrelay
+
+import (
+	"log"
+	"sync"
+)
+
+// Lifecycle owns the shim's start/stop so the global app-email toggle can take effect
+// at runtime without a controller restart. The shim listens ONLY when app-email is
+// globally ON (Part 1: "start listeners only when hub.enabled and global app-email ON").
+// Apply is idempotent: enabling when already up (or disabling when already down) is a
+// no-op.
+type Lifecycle struct {
+	mu      sync.Mutex
+	opts    Options
+	srv     *Server
+	logger  *log.Logger
+	stopped bool // Close was called; further Apply(true) is refused (shutdown)
+}
+
+// NewLifecycle prepares (but does not start) a shim from the given options.
+func NewLifecycle(opts Options) *Lifecycle {
+	lg := opts.Logger
+	if lg == nil {
+		lg = log.Default()
+	}
+	return &Lifecycle{opts: opts, logger: lg}
+}
+
+// Apply reconciles the shim's running state with the desired toggle value. It returns
+// an error only if a requested START failed (a stop never errors meaningfully).
+func (l *Lifecycle) Apply(enabled bool) error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	if l.stopped {
+		return nil
+	}
+	if enabled {
+		if l.srv != nil {
+			return nil // already running
+		}
+		srv, err := New(l.opts)
+		if err != nil {
+			return err
+		}
+		if err := srv.Start(); err != nil {
+			return err
+		}
+		l.srv = srv
+		l.logger.Printf("[INFO] [mailrelay] app-email shim ON (host=%s plain=%s tls=%s)",
+			l.opts.ServiceName, srv.PlainAddr(), srv.TLSAddr())
+		return nil
+	}
+	// disabled → stop if running
+	if l.srv != nil {
+		_ = l.srv.Close()
+		l.srv = nil
+		l.logger.Printf("[INFO] [mailrelay] app-email shim OFF")
+	}
+	return nil
+}
+
+// Running reports whether the shim is currently listening.
+func (l *Lifecycle) Running() bool {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	return l.srv != nil
+}
+
+// Close stops the shim permanently (shutdown). Idempotent.
+func (l *Lifecycle) Close() {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.stopped = true
+	if l.srv != nil {
+		_ = l.srv.Close()
+		l.srv = nil
+	}
+}