feat(wizard): prompt for MusicBrainz/AcoustID contact email

Replace the hardcoded MUSICBRAINZ_USER_AGENT placeholder in env.template
with an optional MUSICBRAINZ_OWNER_EMAIL prompt in step_enrichment.
The backend now composes a valid User-Agent from app name + version +
this email (falling back to the project URL if left blank).

deploy.sh

@@ -38,6 +38,7 @@ CFG_PUBLIC_API_BASE_URL="/api/v1"
 CFG_ADMIN_CREATE="no"; CFG_ADMIN_USER=""; CFG_ADMIN_PASS=""
 CFG_ML_URL=""
 CFG_ACOUSTID_KEY=""
+CFG_MUSICBRAINZ_OWNER_EMAIL=""
 CFG_JWT_SECRET=""
 
 # ==========================================================================
@@ -190,6 +191,8 @@ step_enrichment() {
     ui_title "$(t step_enrichment)"
     ui_dim "$(t enrichment_note)"
     ui_input "$(t acoustid_prompt)" "" ""; CFG_ACOUSTID_KEY="$UI_VALUE"
+    ui_dim "$(t musicbrainz_note)"
+    ui_input "$(t musicbrainz_email_prompt)" "" v_email_opt; CFG_MUSICBRAINZ_OWNER_EMAIL="$UI_VALUE"
 }
 
 access_url() {