Wire Vitest into the existing Vite config (scoped to src/**/*.test.ts so it
never collides with the Playwright suite in tests/) and add test:unit,
test:unit:watch, and test:rust scripts.
Covers the pure logic layer: parseSearchValue prefix parsing, all twelve
sort orders through mergeImages, merge/dedup/window helpers, filter
matching, gallery request tokens, localStorage-backed initial settings,
folder-picker path utilities, and the duplicate/lightbox/gallery/video
formatters. Fixture factories live in src/test/factories.ts.
Break down the monolithic DuplicateFinder component into smaller, highly cohesive modules to improve maintainability and separation of concerns.
- Extract empty, loading, and intro states into dedicated components (`DuplicateFinderEmptyStates`).
- Extract the complex header and action logic into `DuplicateFinderHeader`.
- Move `DuplicateGroupCard` to its own dedicated component file.
- Relocate formatting utilities like byte conversion and relative time strings to a dedicated `format.ts` file.
LyAhn