feat(frontend): add header, filter bar, and sorting store for files page
- sorting.ts: per-section sort store (sort field + order) persisted to localStorage
- dsl.ts: build/parse DSL filter strings ({t=uuid,&,|,!,...})
- Header.svelte: sort dropdown, asc/desc toggle, filter toggle button
- FilterBar.svelte: tag token picker with operator buttons, search, apply/reset
- files/+page.svelte: wired header + filter bar, resets pagination on sort/filter change
- vite-mock-plugin.ts: added 5 mock tags for filter bar development
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Masahiko AMANO
27d8215a0a