feat(design): a channel's and a Plex playlist's one action list (C1) — the row's "…", Delete + undo, an action toast's 8 s floor (E28 S3e2)

- Channels: the row's full-history, hide and unsubscribe buttons become its "…" at the row end
  (useChannelActions: open, pin, YouTube, copy name / link, full history or the admin reset,
  hide with an undo toast, unsubscribe behind its danger confirm); the card layout docks the "…"
  beside the name (ChannelLayoutGrid moreKey). The admin reset's confirm now names the reset.
- Plex playlist page: a title, a show group and a season each open the page's one row menu (a
  title's is its usePlexCardActions list plus the removal); no X at rest; removals take an undo
  toast whose Undo puts every row back at its own index in one request (bulk add `positions`);
  j/k walk the visible rows, Delete removes the walked one; rename and delete in the header's "…".
- notify: a toast with an action lives at least 8 s (the owner's call), whatever the toast setting.

frontend/src/lib/notifications.ts

@@ -92,6 +92,10 @@ const HISTORY_KEY = LS.notifHistory;
 const SETTINGS_KEY = LS.notifSettings;
 const MAX_HISTORY = 100;
 const ERROR_TTL = 15000;
+// A toast that carries an action (an "Undo") lives at least this long, whatever the reader's toast
+// time: its button is the only way back, and a 3 s toast leaves no time to reach it (owner, E28).
+// The setting still decides for longer, and "never" still means never.
+export const ACTION_TTL_MIN = 8000;
 
 // 6b: per-account notification settings (persisted by the Settings panel into the
 // server `preferences`, mirrored to localStorage so they apply before login).
@@ -269,7 +273,9 @@ export function notify(input: NotifyInput): number {
       : level === "error" || level === "fatal"
         ? ERROR_TTL
         : config.durationMs > 0
-          ? config.durationMs
+          ? input.action
+            ? Math.max(config.durationMs, ACTION_TTL_MIN)
+            : config.durationMs
           : undefined;
 
   // Coalesce a rapid burst of identical notifications (same level+title+message within the