feat: use ${SUBDOMAIN} variable in all templates

All 51 docker-compose.yml: replaced hardcoded subdomain.${DOMAIN}
with ${SUBDOMAIN}.${DOMAIN} in Traefik labels, app env vars, and
comments.

All 51 .felhom.yml: added SUBDOMAIN deploy field (type: subdomain)
with default matching existing subdomain metadata value.

Works with felhom-controller v0.27.0 which validates and stores the
user-chosen subdomain in app.yaml. Existing deployed apps get
SUBDOMAIN auto-injected via InjectMissingFields() on next sync.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/mealie/.felhom.yml

@@ -29,6 +29,14 @@ deploy_fields:
     description: "A szerver domain neve"
     locked_after_deploy: true
 
+  - env_var: SUBDOMAIN
+    label: "Aldomain"
+    type: subdomain
+    default: "recipes"
+    required: true
+    locked_after_deploy: true
+    description: "Az alkalmazás aldomainje"
+
 # --- App info (info page content) ---
 app_info:
   tagline: 'Receptkezelő és étkezés tervező a családnak'
@@ -47,4 +55,4 @@ app_info:
     - 'Jelentkezz be: changeme@example.com / MyPassword'
     - 'Változtasd meg azonnal az email címet és jelszót'
     - 'Importáld az első receptet egy weboldal URL beillesztésével'
-    - 'Próbáld ki az étkezés tervezőt'
+    - 'Próbáld ki az étkezés tervezőt'

templates/mealie/docker-compose.yml

@@ -1,5 +1,5 @@
 # Mealie - Recipe Manager & Meal Planner
-# Domain: recipes.${DOMAIN}
+# Domain: ${SUBDOMAIN}.${DOMAIN}
 # Database: None (SQLite, built-in)
 # RAM: ~200MB (mem_limit: 1000M) | Pi-compatible: Yes (arm64 only)
 #
@@ -25,7 +25,7 @@ services:
       - TZ=Europe/Budapest
       - MAX_WORKERS=1
       - WEB_CONCURRENCY=1
-      - BASE_URL=https://recipes.${DOMAIN}
+      - BASE_URL=https://${SUBDOMAIN}.${DOMAIN}
     volumes:
       - mealie_data:/app/data/
     networks:
@@ -42,7 +42,7 @@ services:
       start_period: 60s
     labels:
       - "traefik.enable=true"
-      - "traefik.http.routers.mealie.rule=Host(`recipes.${DOMAIN}`)"
+      - "traefik.http.routers.mealie.rule=Host(`${SUBDOMAIN}.${DOMAIN}`)"
       - "traefik.http.routers.mealie.entrypoints=websecure"
       - "traefik.http.routers.mealie.tls=true"
       - "traefik.http.routers.mealie.tls.certresolver=letsencrypt"