feat(ui): E31 S4a — rail rows are links, the channel page opens on unwatched, users and audit tidied

- Nav rail page rows are real links (/?page=<id>): a middle-click or
  Ctrl-click opens the page in a new tab; a plain click stays in-app.
- A fresh channel page shows the unwatched videos; a picked watch state
  is a remembered preference (channelShow).
- Users: the role, suspend and delete move into the row's one menu
  (the "…", right-click, Shift+F10); locked ones keep their reason.
- Audit log: back-to-back successful runs of one job fold into one row
  that opens to the earlier ones; a failed run reads in the danger colour.
- DESIGN.md decision log: the E31 picks.

frontend/src/lib/storage.ts

@@ -35,6 +35,7 @@ export const LS = {
   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",
+  channelShow: "siftlode.channelShow",
   channelDiscoverySort: "siftlode.channelDiscoverySort",
   // Cards-per-page for the card layout (the table keeps its own rows-per-page in its persist blob).
   channelCardSize: "siftlode.channelCardSize",