markAllRead doesn't update per-subscription unread counts in sidebar collections

[brendanlong]

Problem

After markAllRead, the success handler in src/lib/hooks/useEntryMutations.ts:370-384:

1. Invalidates utils.subscriptions.list (React Query cache)
2. Invalidates utils.entries.list (React Query cache)
3. Refetches tags collection
4. Calls refreshGlobalCounts() for "all"/"starred"/"saved" counts

However, per-tag subscription collections (TagSubscriptionsCollection instances in the sidebar) are backed by separate query keys (["subscriptions-tag", filterKey]), which are NOT invalidated by utils.subscriptions.list.invalidate(). This means individual subscription unread counts in the sidebar remain stale until the user collapses and re-expands the tag section.

Fix

After markAllRead, also reset subscription unread counts in the global subscriptions collection (set all to 0 when markAllRead has no filter, or set filtered subscriptions to 0). Additionally, either invalidate the per-tag subscription collection queries or directly update the subscription objects in the per-tag collections.

Related to #580 (tanstack-db branch).

-- Claude