fix(photos): persist uploads via Docker named volume

Photos were lost on redeploy because they wrote to public/uploads
inside the container with no volume mount. Now stored in uploads_data
named volume via UPLOAD_DIR env var (already supported by upload route).

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

docker-compose.yml

@@ -15,7 +15,10 @@ services:
       - db
     ports:
       - "${PORT:-3000}:3000"
+    volumes:
+      - uploads_data:/data/uploads
     environment:
+      UPLOAD_DIR: /data/uploads
       DATABASE_URL: "postgresql://grow:${POSTGRES_PASSWORD}@db:5432/grow"
       NEXTAUTH_URL: ${NEXTAUTH_URL}
       AUTH_SECRET: ${AUTH_SECRET}
@@ -44,3 +47,4 @@ services:
 
 volumes:
   postgres_data:
+  uploads_data: