ci: 更新 CI workflow — setup-uv v7、locked sync、push trigger

- 新增 push: [main] trigger，main 上的 commit 也會執行 CI
- 升級 astral-sh/setup-uv@v5 → @v7，python-version 移入 setup-uv
  （移除多餘的 actions/setup-python 步驟）
- uv sync --dev → uv sync --locked --dev，確保 CI 環境可重現
- pytest 加上 -v --tb=short，失敗時輸出更易讀

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

Author: singyichen

.github/workflows/ci.yml

@@ -1,6 +1,8 @@
 name: CI
 
 on:
+  push:
+    branches: [main]
   pull_request:
     branches: [main]
 
@@ -13,15 +15,12 @@ jobs:
         working-directory: backend
     steps:
       - uses: actions/checkout@v4
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v7
         with:
-          version: "latest"
+          python-version: "3.12"
           enable-cache: true
           cache-dependency-glob: "backend/uv.lock"
-      - uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-      - run: uv sync --dev
+      - run: uv sync --locked --dev
       - run: uv run ruff check .
       - run: uv run ruff format --check .
 
@@ -33,15 +32,12 @@ jobs:
         working-directory: backend
     steps:
       - uses: actions/checkout@v4
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v7
         with:
-          version: "latest"
+          python-version: "3.12"
           enable-cache: true
           cache-dependency-glob: "backend/uv.lock"
-      - uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-      - run: uv sync --dev
+      - run: uv sync --locked --dev
       - run: uv run mypy .
 
   test:
@@ -52,13 +48,10 @@ jobs:
         working-directory: backend
     steps:
       - uses: actions/checkout@v4
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v7
         with:
-          version: "latest"
+          python-version: "3.12"
           enable-cache: true
           cache-dependency-glob: "backend/uv.lock"
-      - uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-      - run: uv sync --dev
-      - run: uv run pytest --cov=app --cov-report=term-missing
+      - run: uv sync --locked --dev
+      - run: uv run pytest -v --tb=short --cov=app --cov-report=term-missing