feat(library): show view count on published clips' cards

[DarrellVS]

Closes #63.

What

A published clip's card shows how often it has been opened, last on the metadata line: 0:21 · Battlefield 6 · 2 days ago · 87.2 MB · 37 views. Hover shows when it was last opened.

How

• No per-page fetch. publisherViews / publisherLastViewedAt were already mirrored onto every row by SyncPublisherStatsAction and already in ClipDTO, so every library page carries them.
• Freshness was the gap. The sync ran at boot and on the Publisher screen only. useLibraryViewCounts now asks on library open and on window focus with maxAgeMs; main answers from the last attempt when it is inside ten minutes (statsAreStale, one clock shared by every caller, attempts count as well as successes) and collapses concurrent calls onto the one in flight. The Publisher screen passes nothing and always asks, as before.
• Patch, not refetch. clipsStore.applyPublisherViews assigns the two fields on rows already on screen, after the page's own first fetch has landed, so the grid does not jump and the requestId pattern is not raced.
• Quiet on failure. An unreachable publisher leaves the last numbers; the Publisher screen is where that is explained.
• Null and zero both say nothing on a card. A card cannot tell "never opened" from "nothing was counting yet"; the Publisher screen knows countingSince and says both.

Testing

• npm run check: typecheck and 875 unit tests green. New: viewCount.spec.ts (label) and publisherStatsFreshness.spec.ts (throttle). The zero rule was mutated to confirm its test fails.
• e2e not run and no e2e spec added: the suite is being reworked in parallel.

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