[Security hardening] Add automated security audit workflow

.github/workflows/security.yml

@@ -0,0 +1,51 @@
+name: Security Audit
+
+permissions:
+  contents: read
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+  schedule:
+    - cron: "17 4 * * 1"
+  workflow_dispatch:
+
+jobs:
+  dependency-audit:
+    name: Dependency audit
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b # v8.1.0
+
+      - name: Set up Python
+        uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6
+        with:
+          python-version: "3.13"
+
+      - name: Run pip-audit
+        run: uvx pip-audit . --progress-spinner off
+
+  static-analysis:
+    name: Static analysis
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b # v8.1.0
+
+      - name: Set up Python
+        uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6
+        with:
+          python-version: "3.13"
+
+      - name: Run Bandit
+        # B602 is tracked in #2440; keep the baseline green until shell steps
+        # require explicit opt-in.
+        run: uvx bandit -r src -lll --skip B602