feat(managers): shared sort across the table and card layouts

Cards have no column headers to sort by, so lift the sort out of DataTable into
one shared state that BOTH views drive and reflect. New lib/columnSort.ts holds
the comparator + click-cycle (one source of truth); DataTable gains an optional
controlled sort (sort + onSortChange) and falls back to its internal persistKey
sort when they're omitted, so every other table is untouched. The subscribed
sort lives in ChannelsProvider, discovery keeps its own (its columns differ);
a new ColumnSortControl dropdown (options derived from the columns' sortable
metadata, feed-style + asc/desc toggle) drives it in cards mode. Per-account,
persisted, per-tab.

frontend/src/lib/storage.ts

@@ -24,8 +24,11 @@ export const LS = {
   feedView: "siftlode.feedView",
   channelFilter: "siftlode.channelFilter",
   channelsView: "siftlode.channelsView",
-  // The channel manager's layout (table / cards / rows — see lib/channelLayout.ts), per-account.
+  // The channel manager's layout (table / cards — see lib/channelLayout.ts), per-account.
   channelLayout: "siftlode.channelLayout",
+  // The manager's sort, lifted out of the table so the card layout shares it (per-account, per-tab).
+  channelSort: "siftlode.channelSort",
+  channelDiscoverySort: "siftlode.channelDiscoverySort",
   channelsTable: "siftlode.channelsTable",
   channelDiscoveryTable: "siftlode.channelDiscoveryTable",
   settingsTab: "siftlode.settingsTab",