chore: replace npm/npx references with bun/bunx

[BertVermorgen]

Summary

• Replace npx playwright* and npx vitest* with bunx equivalents in .claude/settings.json
• Replace npx playwright install with bunx playwright install in CI workflow
• Remove (npm) label from GitHub Packages auth step name in CI workflow
• Replace npx lint-staged with bunx lint-staged in husky pre-commit hook
• Replace npm run dev with bun run dev in playwright.config.ts webServer config
• Replace npm run test:e2e with bun run test:e2e in error messages in global-setup.ts

Note: .npmrc files are intentionally unchanged — they configure the GitHub Packages registry URL (an npm-protocol registry), which bun reads natively.

Closes #10

Test plan

• Verify CI pipeline passes (bun install, build, test, e2e)
• Verify pre-commit hook runs bunx lint-staged correctly
• Verify Playwright e2e tests launch dev server with bun run dev

🤖 Generated with Claude Code

[BertVermorgen]

AI Review: Code looks good. ✓

All changes are correct mechanical replacements of npm/npx with bun/bunx:

• bunx is the correct bun equivalent of npx
• bun run is the correct replacement for npm run
• .npmrc files correctly left unchanged — bun reads them natively for registry config

No logic errors, security issues, or anti-patterns introduced.