feat(channels,datatable): unify sync-status into one controlled DataTable filter (R13 S2a)

The top sync chips and the Sync column's own select filter were two independent
states with different vocab (all/needs_full/fully_synced vs fully/needsFull) and
subtly different semantics. DataTable gains a controlled filters/onFiltersChange
pair (symmetric to the existing controlled sort); ChannelsProvider now owns the
filter map via a new useFilterState hook, so the top chips, the Sync column
funnel, the card layout, and the header "full history" deep-link all drive ONE
filters.sync. The card layout reuses the exported filterRows predicate instead of
its own status pre-filter. Vocab unified on the column's fully = recent_synced &&
backfill_done, which now matches the Sync cell's own "fully synced" badge.

frontend/src/lib/storage.ts

@@ -22,7 +22,10 @@ export const LS = {
   // until /api/me lands: the account isn't pinned yet (App pins it once meQuery resolves), so
   // the per-account key can't be read.
   feedView: "siftlode.feedView",
-  channelFilter: "siftlode.channelFilter",
+  // The subscribed table's column filters (a FilterMap), lifted out of the table so the top status
+  // chips, the Sync column funnel, and the card layout all share ONE state (per-account). Supersedes
+  // the old single-string `channelFilter` sync chip.
+  channelsFilterMap: "siftlode.channelsFilterMap",
   channelsView: "siftlode.channelsView",
   // The channel manager's layout (table / cards — see lib/channelLayout.ts), per-account.
   channelLayout: "siftlode.channelLayout",