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.sum

@@ -1,5 +1,9 @@
 github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
 github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+mFykh5fBlto=
+github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6 h1:oP4q0fw+fOSWn3DfFi4EXdT+B+gTtzx8GC9xsc26Znk=
+github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
+github.com/emersion/go-smtp v0.24.0 h1:g6AfoF140mvW0vLNPD/LuCBLEAdlxOjIXqbIkJIS6Wk=
+github.com/emersion/go-smtp v0.24.0/go.mod h1:ZtRRkbTyp2XTHCA+BmyTFTrj8xY4I+b4McvHxCU2gsQ=
 github.com/google/pprof v0.0.0-20250317173921-a4b03ec1a45e h1:ijClszYn+mADRFY17kjQEVQ1XRhq2/JR1M3sGqeJoxs=
 github.com/google/pprof v0.0.0-20250317173921-a4b03ec1a45e/go.mod h1:boTsfXsheKC2y+lKOCMpSfarhxDeIzfZG1jqGcPl3cA=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=