Feed writes: bulk OPML upsert, targeted fetch-result update, shared toggle

- AddFeedScreen: OPML import no longer crashes the app on a
  non-XML/corrupt file (try/catch around the whole import). Bulk
  upsertAll() instead of a per-feed getById()+upsert() loop -- 2N
  sequential DB round-trips for N feeds otherwise, real cost at 100+
  feed subscription lists.
- FeedDao.updateFetchResult only writes the columns a fetch actually
  produces, instead of a full-row @Update built from a feed snapshot
  read before a (possibly slow) network round-trip -- the old path
  could silently revert a readerModeEnabled/folder edit made via
  FeedListScreen while that feed's fetch was still in flight.
- setReaderModeEnabled(feed, enabled) persists the toggle and returns
  the exact confirmation text, shared by FeedListScreen's per-row
  toggle and ReaderScreen's toggleFeedReaderMode -- previously two
  independently-typed copies of the same snackbar message.

0 files changed, 0 insertions, 0 deletions