Implement infinite-scroll pagination on MediaGridScreen, episode list, and my shares

- MediaGridScreen: adds ScrollController+CustomScrollView; limit/offset params
  (page size 50); generation counter guards stale _loadMore results; shows
  CircularProgressIndicator at bottom while loading, "No more items" when done.
- PodcastEpisodesScreen: adds NotificationListener<ScrollNotification> outside
  RefreshIndicator (avoids ListView+controller interference with overscroll);
  limit/offset (page size 50); same generation counter pattern; shows
  footer spinner or "All episodes loaded" message.
- MySharesScreen: adds end-of-list "All shares loaded" indicator after first
  successful fetch (shares API returns all items in a single response, no
  server-side pagination available).
- Pull-to-refresh resets offset=0 and hasMore=true on all three screens.
- All 362 existing tests pass; flutter analyze reports no issues.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions