docs: clarify VITE_API_URL usage; remove FRONTEND_API_URL; add storage vars; simplify compose mounts and external DB example (refs #18)

.env.example

@@ -34,9 +34,15 @@ SMTP_PASS=your-app-specific-password
 EMAIL_FROM=noreply@yourdomain.com
 
 # Application URLs
+# Use full origin with scheme, no trailing slash.
+# Admin UI is served by the frontend at /admin.
 FRONTEND_URL=https://yourdomain.com
-ADMIN_URL=https://yourdomain.com:3001
-VITE_API_URL=https://yourdomain.com:3001/api
+ADMIN_URL=https://yourdomain.com
+
+# Frontend API base
+# For pre-built images and production behind a reverse proxy, keep '/api'.
+# If you rebuild the frontend yourself, you may set a full URL at build time.
+VITE_API_URL=/api
 
 # Port Configuration (optional)
 # BACKEND_PORT=3001
@@ -50,4 +56,16 @@ TZ=UTC
 # Analytics (Optional - Umami)
 VITE_UMAMI_URL=
 VITE_UMAMI_WEBSITE_ID=
-VITE_UMAMI_SHARE_URL=
+VITE_UMAMI_SHARE_URL=
+
+# Storage variables (host paths)
+# These control where data is stored on the host. Defaults are local folders.
+APP_STORAGE=./storage
+APP_DATA=./data
+LOGS=./logs
+
+# Note on FRONTEND_API_URL (documentation only):
+# When using pre-built frontend images, runtime env vars cannot override the built JS.
+# Do NOT rely on FRONTEND_API_URL in Compose. Instead, keep VITE_API_URL=/api and
+# let the frontend Nginx proxy /api to the backend. Only if you rebuild the frontend
+# should you change VITE_API_URL at build time.