Keep the database in ./data and bind-mount it

SQLite writes three files — the database plus its -wal and -shm companions.
Putting them in one directory means a deployment mounts a single path and a
backup copies a single directory.

- FOODSTER_DB defaults to ./data/foodster.db, and openDB creates the parent
  directory on startup rather than failing on a fresh checkout
- compose bind-mounts ./data instead of using a named volume, so the file can
  be listed, copied and opened with any sqlite client without going through
  the container engine
- the image runs as UID 65534, which cannot write to a host directory owned
  by someone else, so compose now sets user: from FOODSTER_UID/FOODSTER_GID
- `make up` creates ./data first: left to the engine it appears root-owned
  and the app silently cannot write to it

compose.yaml

@@ -2,6 +2,11 @@ services:
   app:
     image: ${FOODSTER_REPO:?set FOODSTER_REPO in .env}:${FOODSTER_TAG:-latest}
     restart: unless-stopped
+    # A bind mount rather than a named volume: the database sits in ./data on
+    # the host, where it can be listed, copied and backed up without going
+    # through the container engine. The image runs as UID 65534, so the
+    # container has to be told which host user owns that directory.
+    user: "${FOODSTER_UID:-1000}:${FOODSTER_GID:-1000}"
     ports:
       - "${FOODSTER_PORT:-8080}:8080"
     environment:
@@ -9,7 +14,4 @@ services:
       FOODSTER_DB: /data/foodster.db
       TZ: ${TZ:-Europe/Helsinki}
     volumes:
-      - foodster-data:/data
-
-volumes:
-  foodster-data:
+      - ./data:/data