fix: use named Docker volume for uploads to fix permission errors

Bind-mounting ./data/uploads caused EACCES errors because Docker creates
the host directory as root, while the container runs as nextjs (UID 1001).
A named volume is initialized from the image where chown is already set correctly.

docker-compose.yml

@@ -28,7 +28,7 @@ services:
     expose:
       - "3000"
     volumes:
-      - ./data/uploads:/app/public/uploads
+      - uploads:/app/public/uploads
 
   mailpit:
     image: axllent/mailpit:latest
@@ -46,6 +46,9 @@ services:
       - ./Caddyfile:/etc/caddy/Caddyfile:ro
       - ./data/caddy/data:/data
       - ./data/caddy/config:/config
-      - ./data/uploads:/srv/uploads
+      - uploads:/srv/uploads
     depends_on:
       - app
+
+volumes:
+  uploads: