ci(security): add cargo-audit job (weekly + on push)

.woodpecker.yml

@@ -16,6 +16,25 @@ steps:
       - cargo clippy --workspace --all-features -- -D warnings
       - cargo test --workspace --all-features
 
+---
+kind: pipeline
+name: security-audit
+
+when:
+  event:
+    - push
+    - cron
+  branch:
+    - dev
+  cron: weekly-security
+
+steps:
+  - name: cargo-audit
+    image: rust:1.83
+    commands:
+      - cargo install cargo-audit --locked
+      - cargo audit
+
 ---
 kind: pipeline
 name: release