Switch Docker volume to bind mount at /home/christoph/fitnesspad

Makes the database directly accessible on the host filesystem instead
of an opaque Docker volume.

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

docker-compose.yml

@@ -4,8 +4,5 @@ services:
     ports:
       - "8090:8090"
     volumes:
-      - db-data:/data
+      - /home/christoph/fitnesspad:/data
     restart: unless-stopped
-
-volumes:
-  db-data: