The web reader had all the infrastructure for progress persistence
(updateReadingProgress/getReadingProgress API functions, PUT/GET
endpoints, database queries) but the reader.ts never called them.
Changes:
- Add debounced (2s) saveProgress call on every relocate event that
PUTs percentage, current_page, total_pages, and epubcfi to the
existing /api/media-items/:id/progress endpoint
- Replace renderer.next() with view.init({ lastLocation }) to restore
the reader to the last saved position on load (CFI first, then
fraction fallback, then default first page)
- Pass savedPercentage and savedCfi from server-side progress data
through readerInitExpr config to the JS initReader function
- Add mediaItemId and saveTimeout to the Alpine data object
This fixes both the blank /progress page and the missing progress
section on book detail pages — both were empty because the
reading_progress table never received any data from the web reader.