Use bind mount for lnbits data instead of named volume

This allows easier seeding and management of lnbits data:
- data/lnbits/ for runtime data
- data/lnbits-seed/ for pre-populated seed data

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -19,7 +19,7 @@ services:
     ports:
       - 5001:5001
     volumes:
-      - lnbits-data:/app/data
+      - ./data/lnbits:/app/data
       - ./data/lnd-3:/app/lnd:uid=1000,gid=1000
 
   boltz:
@@ -422,7 +422,6 @@ services:
       - elements-data:/root/.elements
 
 volumes:
-  lnbits-data:
   bitcoin-data:
   elements-data:
   nginx-data: