cleanup(legibility): repo hygiene — untrack artifacts, update gitignore

CLEANUP-4 (#415):

Untracked from git (files stay on disk where appropriate):
- frontend/e2e/.auth/user.json — dev credential, already gitignored in
  frontend/.gitignore; git rm --cached so the rule takes effect
- proofshot-artifacts/ (44 files, ~7.6MB) — browser verification
  screenshots committed by mistake; added root .gitignore entry
- frontend/.svelte-kit.old/ — stale type stub from stammbaum route
  rename; deleted from disk
- frontend/test-results.locked/ — Playwright E2E artifacts; deleted
  from disk
- node_modules/.vite/vitest/.../results.json — Vite test cache committed
  by mistake

Deleted from repo:
- package.json / package-lock.json at root (3 testing-library devDeps
  with no justification for living outside frontend/)

.gitignore additions:
- root: proofshot-artifacts/, node_modules/
- frontend: **/test-results.locked/, **/.svelte-kit.old/

After this commit, git status on a fresh clone shows zero unexpected
items (only docs/superpowers/ and familienarchiv-408/ remain untracked,
both pre-existing).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -18,5 +18,11 @@ scripts/large-data.sql
 .claude/worktrees/
 .claude/scheduled_tasks.lock
 
+# Run artifacts from verification tooling
+proofshot-artifacts/
+
+# Root-level Node.js tooling artifacts
+node_modules/
+
 # Repo uses npm; yarn.lock is ignored to avoid double-lockfile drift.
 frontend/yarn.lock