feat: always-optimistic write pattern across all repos

All create/update/delete repo methods now write to IndexedDB optimistically
and fire mutationQueue.flush() as fire-and-forget, returning immediately
without waiting for the network. This eliminates the 8-second UX freeze
previously seen when the API was unreachable but navigator.onLine was true.

- Repos rewritten: trip, day, place, packing, todo, budget, accommodation,
  reservation, file — write methods never throw, always return optimistic data
- mutationQueue.flush() changed to iterative (one item per loop iteration)
  so mutations enqueued mid-flush (e.g. bulk check-all) are picked up
- fileRepo.toggleStar skips the IDB put when the file is not cached locally
- DayDetailPanel passes place_name into accommodationRepo.create so the
  optimistic accommodation renders the correct hotel label immediately
- Test suite updated throughout to reflect optimistic-first semantics:
  no more rollback assertions, IDB cleared in component test beforeEach hooks,
  FileManager tests switched from filesApi spy to MSW endpoint assertions

client/src/components/Planner/DayDetailPanel.tsx

@@ -118,8 +118,10 @@ export default function DayDetailPanel({ day, days, places, categories = [], tri
   const handleSaveAccommodation = async () => {
     if (!hotelForm.place_id) return
     try {
+      const selectedPlace = places.find(p => p.id === hotelForm.place_id)
       const data = await accommodationRepo.create(tripId, {
         place_id: hotelForm.place_id,
+        place_name: selectedPlace?.name,
         start_day_id: hotelDayRange.start,
         end_day_id: hotelDayRange.end,
         check_in: hotelForm.check_in || null,