ci: add CodeQL scanning and PR dependency review

.github/workflows/codeql.yml

@@ -0,0 +1,53 @@
+name: CodeQL
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  schedule:
+    # Weekly scan so new CodeQL queries run even without pushes
+    - cron: '26 7 * * 1'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  analyze:
+    name: Analyze (java-kotlin)
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      security-events: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          java-version: 17
+          distribution: temurin
+          cache: gradle
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: java-kotlin
+          build-mode: manual
+
+      # Kotlin extraction requires a real compilation; assembleDebug is the
+      # cheapest target that compiles every module.
+      - name: Build for analysis
+        run: |
+          chmod +x gradlew
+          touch local.properties
+          echo "apiKey=\"\"" >> local.properties
+          ./gradlew assembleDebug
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: '/language:java-kotlin'

.github/workflows/dependency-review.yml

@@ -0,0 +1,20 @@
+name: Dependency review
+
+# Flags PRs that introduce dependencies with known vulnerabilities.
+on:
+  pull_request:
+    branches: [ master ]
+
+permissions:
+  contents: read
+
+jobs:
+  dependency-review:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - name: Dependency review
+        uses: actions/dependency-review-action@v4
+        with:
+          fail-on-severity: high