feat: saved views frontend hook, panel, and Findings integration (#235)

[khat190]

What Changed

• frontend/src/hooks/useSavedViews.ts — Custom hook managing full preset CRUD. Writes to localStorage immediately (offline-safe) and syncs to /api/v1/saved-views when the backend is reachable. Validates every preset on read so corrupt data is silently dropped. Includes doc comment explaining exact sync failure behaviour.
• frontend/src/components/SavedViewsPanel.tsx — Dropdown panel in the Findings filter row. Save current filters under a name, apply in one click, inline rename, two-click delete with confirm guard.
• frontend/src/pages/Findings.tsx — Minimal diff on the original. Added hook, currentPreset snapshot, applyPreset helper, and SavedViewsPanel next to Reset Filters. Everything else untouched.
• frontend/testing/unit/hooks/useSavedViews.test.ts — 28 tests covering all CRUD operations, localStorage persistence, corrupt data handling, and validation.
  - frontend/testing/unit/pages/Findings.test.tsx — Updated tests matching the existing Findings UI.

Depends on: feat/saved-views-backend (PR #403) for backend persistence. Works standalone via localStorage if backend is unavailable.

Refs #235

Screenshots:

[utksh1]

Holding this frontend companion PR until the saved-views backend contract in #403 is fixed. The UI and hook work depends on /api/v1/saved-views, and merging the frontend first would leave the feature in localStorage fallback mode with the server path still unreliable. Please rebase once #403 is corrected and make sure the frontend tests still pass against the finalized response and error contract.