CI: add npm build workflow; fix shop field mismatch (server sends 'value', client used nonexistent 'buy_price') and strict-mode TS errors

.gitea/workflows/build.yml

@@ -0,0 +1,20 @@
+name: build
+on: [push, workflow_dispatch]
+
+jobs:
+  build-test:
+    runs-on: docker
+    container: node:20-bookworm
+    timeout-minutes: 15
+    steps:
+      - name: Checkout
+        run: git clone --depth 1 ${{ github.server_url }}/${{ github.repository }}.git .
+
+      - name: Install
+        run: npm ci || npm install
+
+      - name: Build
+        run: npm run build
+
+      - name: Test
+        run: npm test --if-present