fixes for double nginx forward scenarios

backend/app/config.py

@@ -35,6 +35,11 @@ class Settings(BaseSettings):
     # Theme export
     WEBSITE_URL: str = "https://kmountainflower.org"
     THEME_JSON_PATH: str = "/app/theme.json"
+    STATIC_FILES_DIR: str = "/usr/share/nginx/html"
+    # Internal URL for fetching static files when they're not on the local
+    # filesystem (e.g. separate Docker/K8s containers). Falls back to
+    # WEBSITE_URL if not set.
+    STATIC_UPSTREAM_URL: str = ""
 
     model_config = {"env_prefix": "KMTN_"}