feat(ci): add dependabot, codeql and dependency review gates

.github/dependabot.yml

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+# Dependabot 依赖更新门禁
+# 安全更新（security updates）按单条 PR 处理，不进入 groups（applies-to: version-updates 限定分组范围）
+version: 2
+updates:
+  - package-ecosystem: maven
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday
+      time: "03:00"
+      timezone: "Asia/Shanghai"
+    open-pull-requests-limit: 10
+    labels:
+      - "dependencies"
+    groups:
+      maven-minor-patch:
+        applies-to: version-updates
+        update-types:
+          - minor
+          - patch
+
+  - package-ecosystem: npm
+    directory: "/frontend"
+    schedule:
+      interval: weekly
+      day: monday
+      time: "03:00"
+      timezone: "Asia/Shanghai"
+    open-pull-requests-limit: 10
+    labels:
+      - "dependencies"
+    groups:
+      npm-minor-patch:
+        applies-to: version-updates
+        update-types:
+          - minor
+          - patch

.github/workflows/codeql.yml

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+# CodeQL 静态安全扫描
+# 语言选择：java-kotlin（Maven 多模块，autobuild 走 ./mvnw）与 javascript-typescript（前端，无需构建）
+# queries 用 security-and-quality：在默认规则集之上叠加 security-extended，换取更全的漏洞与质量覆盖
+name: "CodeQL"
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+  schedule:
+    - cron: '23 18 * * 1'
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+    permissions:
+      security-events: write
+      actions: read
+      contents: read
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: java-kotlin
+            build-mode: autobuild
+          - language: javascript-typescript
+            build-mode: none
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      # autobuild 依赖 ./mvnw 编译，必须显式提供 temurin 17，否则默认 JDK 可能不匹配 pom.xml
+      - name: Set up JDK 17
+        if: matrix.language == 'java-kotlin'
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 17
+          cache: maven
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+          queries: security-and-quality
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:${{matrix.language}}"

.github/workflows/dependency-review.yml

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+# Dependency Review 依赖审查
+# 在 PR 上对比依赖清单差异，命中 high 及以上严重级别漏洞即失败（fail-on-severity: high）
+# Maven pom.xml 与 frontend/package-lock.json 由 action 自动发现，无需额外配置
+name: "Dependency Review"
+
+on:
+  pull_request:
+
+permissions:
+  contents: read
+  pull-requests: write
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  dependency-review:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - name: "Checkout Repository"
+        uses: actions/checkout@v4
+
+      - name: "Dependency Review"
+        uses: actions/dependency-review-action@v4
+        with:
+          fail-on-severity: high