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

Makefile

@@ -31,10 +31,8 @@ build: generate ## Build ./foodster
 	CGO_ENABLED=0 go build -trimpath \
 		-ldflags="-s -w -X main.version=dev" -o $(BIN) $(PKG)
 
-run: generate ## Run locally on :8080
-	FOODSTER_PASSWORD=$${FOODSTER_PASSWORD:-dev} \
-	FOODSTER_DB=$${FOODSTER_DB:-./foodster.db} \
-	go run $(PKG)
+run: generate ## Run locally on :8080 (database in ./data)
+	FOODSTER_PASSWORD=$${FOODSTER_PASSWORD:-dev} go run $(PKG)
 
 seed: ## Import a dish bundle (SEED=seeds/testi.json)
 	go run $(PKG) -import $(SEED)
@@ -84,6 +82,7 @@ push: ## Push the newest tag and :latest
 release: image push ## Build, tag and push in one go
 
 up: ## Start the stack
+	@mkdir -p data   # or the engine creates it root-owned and the app cannot write
 	$(COMPOSE) up -d
 
 down: ## Stop the stack