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/go.mod

@@ -3,6 +3,8 @@ module gitea.dooplex.hu/admin/felhom-controller
 go 1.24.0
 
 require (
+	github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6
+	github.com/emersion/go-smtp v0.24.0
 	golang.org/x/crypto v0.31.0
 	gopkg.in/yaml.v3 v3.0.1
 	modernc.org/sqlite v1.45.0