fix: add missing /app/data volume for SQLite migration

The data volume was missing in dev environment, preventing automatic
SQLite → PostgreSQL migration. The SQLite database (bodytrack.db) was
not accessible to the container, so migration was skipped.

This fixes the "No SQLite database found" message when data exists.

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

docker-compose.dev-env.yml

@@ -27,6 +27,7 @@ services:
       postgres-dev:
         condition: service_healthy
     volumes:
+      - bodytrack_bodytrack-data:/app/data
       - bodytrack_bodytrack-photos:/app/photos
     environment:
       # Database
@@ -65,5 +66,7 @@ services:
 
 volumes:
   mitai_dev_postgres_data:
+  bodytrack_bodytrack-data:
+    external: true
   bodytrack_bodytrack-photos:
     external: true