feat(test): Week 3 质量保障体系 — 55 新增测试 + CI/CD 流水线

前端第二批测试 (42 用例):
- AuthBloc: 16 用例 (启动恢复/登录/注册/角色选择/班级码/登出)
- HomeBloc: 8 用例 (数据加载/今日检测/心情统计/连续天数/离线容错)
- CalendarBloc: 10 用例 (月份切换/日期选择/视图模式/状态保持)
- MoodBloc: 8 用例 (统计加载/周期切换/API解析/错误处理)

后端 P0 单元测试 (13 用例):
- journal_service: 5 用例 (model_to_resp 转换/mood回退/weather回退/tags解析)
- sync_service: 8 用例 (冲突收集/DTO构造/序列化roundtrip/非冲突排除)

CI/CD:
- pr-check.yml: PR 触发 cargo fmt+check+clippy+test + flutter analyze+test
- main-merge.yml: main push 触发完整检查 + cargo audit 安全审计

测试统计: 前端 84 通过, 后端 73 通过 (全部通过)

.github/workflows/main-merge.yml

@@ -0,0 +1,54 @@
+name: Main Merge
+on:
+  push:
+    branches: [main]
+
+jobs:
+  backend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: crates → target
+
+      - name: cargo fmt
+        run: cargo fmt --all -- --check
+
+      - name: cargo check
+        run: cargo check --all-targets
+
+      - name: cargo clippy
+        run: cargo clippy --all-targets -- -D warnings
+
+      - name: cargo test
+        run: cargo test --all
+
+      - name: cargo audit  # 安全审计（可选，允许失败）
+        run: |
+          cargo install cargo-audit 2>/dev/null || true
+          cargo audit || true
+
+  frontend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: subosito/flutter-action@v2
+        with:
+          flutter-version: '3.x'
+          channel: 'stable'
+
+      - name: Install dependencies
+        run: flutter pub get
+        working-directory: app
+
+      - name: flutter analyze
+        run: flutter analyze --no-fatal-infos
+        working-directory: app
+
+      - name: flutter test
+        run: flutter test
+        working-directory: app

.github/workflows/pr-check.yml

@@ -0,0 +1,56 @@
+name: PR Check
+on:
+  pull_request:
+    branches: [main]
+    types: [opened, synchronize, reopened]
+
+jobs:
+  # 后端检查
+  backend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: crates → target
+
+      - name: cargo fmt
+        run: cargo fmt --all -- --check
+        working-directory: .
+
+      - name: cargo check
+        run: cargo check --all-targets
+        working-directory: .
+
+      - name: cargo clippy
+        run: cargo clippy --all-targets -- -D warnings
+        working-directory: .
+
+      - name: cargo test
+        run: cargo test --all
+        working-directory: .
+
+  # 前端检查
+  frontend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: subosito/flutter-action@v2
+        with:
+          flutter-version: '3.x'
+          channel: 'stable'
+
+      - name: Install dependencies
+        run: flutter pub get
+        working-directory: app
+
+      - name: flutter analyze
+        run: flutter analyze --no-fatal-infos
+        working-directory: app
+
+      - name: flutter test
+        run: flutter test
+        working-directory: app