Add test and security baseline

- make quick/check/mutation from cj/security-baseline (Makefile unchanged,
  settings in baseline.mk), pre-commit, gitleaks, Semgrep rules, ESLint
  security rules, Forgejo workflow
- tests/security: generic baseline tests plus app config and role tests
  against createApp() with an in-memory database
- extract createApp() from src/server/index.ts; LB_DATABASE_PATH for tests
- fix gaps found by the tests: reject unknown fields on project create,
  answer malformed JSON with 400 instead of 500, set nosniff on the API
- npm audit fix (next 16.4.1 and others, no high/critical left)
- clear ESLint errors, safeFileName without control-character regex
- per-project ownership stays an open, documented gap (idorGap -> TODO)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/frontend/components/circuit-tree-editor.tsx

@@ -3252,7 +3252,7 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
             showLabel
           />
           <IconButton
-            disabled={!Boolean(sortState) && !hasActiveFilters}
+            disabled={!sortState && !hasActiveFilters}
             icon={FilterX}
             label="Sortierung/Filter zurücksetzen"
             onClick={clearSortAndFilters}