feature/parallel searches

[codebude]

• Support multiple parallel searches in the add book dialog
• Share medium and acquisition status across parallel search panels
• Focus newly added parallel search panels
• Give each parallel search panel a distinct color accent

[github-actions]

🧪 Test Results — 39a09a3

✅ Backend (pytest) — 1039 passed, 0 failed, 0 skipped (1039 total)
✅ CLI (pytest) — 54 passed, 0 failed, 0 skipped (54 total)
✅ Frontend (vitest) — 536 passed, 0 failed, 0 skipped (536 total)
✅ E2E (Playwright) — 79 passed, 0 failed, 0 skipped (79 total)

Summary: ✅ All 1708 tests passed