fix(ci): scope dependency-audit npm audit to runtime deps

The dependency-audit job failed on vulnerabilities from `shadcn` and its
transitive tree (hono, fast-uri, body-parser, @modelcontextprotocol/sdk).
`shadcn` is a build-time scaffolding CLI plus a CSS `@import`, never shipped
in the browser bundle, so it belongs in devDependencies.

- move `shadcn` to devDependencies (regenerated lockfile: dev flags only,
  no version changes)
- run `npm audit` with `--omit=dev`, matching the runtime-only intent of the
  pip-audit step

npm audit --omit=dev --audit-level=high now reports 0 vulnerabilities; the
production build still resolves the shadcn CSS import.

ha-relevant: no

.github/workflows/security.yml

@@ -31,7 +31,10 @@ jobs:
         with:
           node-version: '20'
       - name: NPM Audit
-        run: cd frontend && npm audit --audit-level=high
+        # --omit=dev: only ship-time deps gate the build. Dev-only tooling
+        # (shadcn CLI and its transitive tree: hono, fast-uri, …) is never
+        # bundled or served, so its advisories must not fail release CI.
+        run: cd frontend && npm audit --omit=dev --audit-level=high
       - uses: actions/setup-python@v5
         with:
           python-version: '3.11'