feat(server): 完成 P3 后端API与回归（D2~D9）

- workflow: 任务详情/转审候选/列表分页字段（D5）
- reimbursements: 列表API + pay凭证字段/幂等增强（D7）
- invoice-pool: 列表/详情API + 上传pending_ocr（D9）
- ocr/audit: mock provider + 回归脚本 + regression-all开关（D2/D3）
- CI: 新增 ci-minimal / ci-regression 工作流（D4）

.github/workflows/ci-minimal.yml

@@ -0,0 +1,37 @@
+name: ci-minimal
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  check-minimal:
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: npm
+          cache-dependency-path: |
+            server/package-lock.json
+            client/package-lock.json
+
+      - name: Install server dependencies
+        working-directory: server
+        run: npm ci
+
+      - name: Install client dependencies
+        working-directory: client
+        run: npm ci
+
+      - name: Run minimal checks
+        run: ./scripts/check-minimal.sh