bump to 0.3.1+v5.1.0

Add env vars introduced upstream across v4.6 → v5.0:
- CONVERSION_UPLOAD_ENABLED (v4.8.5) — recipe override true (upstream default false)
- CONVERSION_FILE_MAX_SIZE / _EXTENSIONS_ALLOWED / _API_* (v4.5.0 source)
- DB_PSYCOPG_POOL_ENABLED (v4.8.1)
- DJANGO_EMAIL_URL_APP (v4.6.0) — recipe sets to https://${DOMAIN}
- MEDIA_AUTH_ORIGINAL_URL_HEADER (v5.0.0)

All except CONVERSION_UPLOAD_ENABLED and DJANGO_EMAIL_URL_APP use the
bare-key defer-to-upstream pattern (like existing LOGGING_LEVEL_*), so
upstream defaults apply unless the operator sets them in .env.

Document all 10 vars (commented) in .env.sample.

compose.yml

@@ -56,6 +56,20 @@ x-common-env: &common-env
   AI_MODEL: llama
   # Collaboration
   COLLABORATION_API_URL: https://$DOMAIN/collaboration/api/
+  # Email app URL (used in email templates; matches recipe DOMAIN)
+  DJANGO_EMAIL_URL_APP: "https://${DOMAIN}"
+  # Conversion (file upload → Yjs via y-provider)
+  CONVERSION_UPLOAD_ENABLED: "${CONVERSION_UPLOAD_ENABLED:-true}"
+  CONVERSION_FILE_MAX_SIZE:
+  CONVERSION_FILE_EXTENSIONS_ALLOWED:
+  CONVERSION_API_ENDPOINT:
+  CONVERSION_API_CONTENT_FIELD:
+  CONVERSION_API_TIMEOUT:
+  CONVERSION_API_SECURE:
+  # Database connection pool
+  DB_PSYCOPG_POOL_ENABLED:
+  # Media auth header (matches recipe nginx by default)
+  MEDIA_AUTH_ORIGINAL_URL_HEADER:
 
 x-postgres-env: &postgres-env
   # Postgresql db container configuration
@@ -91,7 +105,7 @@ services:
       labels:
         - "traefik.enable=false"
         - "coop-cloud.${STACK_NAME}.timeout=${TIMEOUT:-120}"
-        - "coop-cloud.${STACK_NAME}.version=0.3.0+v5.1.0"
+        - "coop-cloud.${STACK_NAME}.version=0.3.1+v5.1.0"
     user: "${DOCKER_USER:-1000}"
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8080"]