feat(player): the YouTube player and the file viewer are named in the address

The player names what it plays in its own history entry (watch, wrel, wtab): a reload or a
bookmark reopens it on the page that hosts it, with that page's list as the queue, or alone
from the catalog (GET /api/videos/{id}/row); a page that hosts none gets the shell's. Back
lands on the page's address without it (useBackToClose's url; ui/Modal passes it on). The
Files viewer and player do the same (fview, fplay). The Plex and channel-manager views are
always written in full, as their fallback is remembered state.

frontend/src/lib/queryKeys.ts

@@ -32,6 +32,7 @@ export const qk = {
   ytSearch: (q?: string | null, count?: number) =>
     q !== undefined ? (["yt-search", q, count] as const) : (["yt-search"] as const),
   videoDetail: (id: string) => ["video-detail", id] as const,
+  videoRow: (id: string) => ["video-row", id] as const,
   related: (id?: string, region?: string) =>
     id !== undefined ? (["related", id, region] as const) : (["related"] as const),
   // This session's confirmed marks per video (lib/progressCache `markVideo`): no fetch behind it.