feat(e24): pin to the comfort shelf from every card and row

S3 wires the shelf's editor. The gesture is the E10 right-click menu, so the
decision "this is comfort media" can be made where the thing is — the feed, a
Plex grid, a channel row, a playlist — rather than only on the page that lists
the shelf.

One shared piece, `components/comfortPin.tsx`: the five pin-kind constructors,
the shelf query, and ONE `ActionMenuItem` that switches Pin/Unpin honestly (and
says "not known yet" with a disabled row until the shelf has answered, since a
confident "Pin" over something already pinned is exactly the quiet lie the house
rules forbid). Surfaces that already have a row menu compose the item in
(`Playlists`, `PlaylistsRail`); the rest mount `ComfortPinMenu`.

Two structural notes:

- The feed's menu lives in `VirtualFeed`, not in `Feed` — that is the list, and
  it is also what gives the channel page the gesture for free, since it renders
  `<Feed channelScoped>` all the way down.
- Cards take `menuProps` as a FUNCTION of the row, not the built props object.
  `triggerProps` is stable across renders while its return value is not, and a
  fresh object prop would blow past `VideoCard`'s memo for every card in the
  virtualized feed on every parent render.

`DataTable` and `ChannelLayoutGrid` grow a generic `rowProps` so a channel row
answers the same gesture in both of the manager's layouts; the table stays
domain-free and never learns what a menu is.

On Home the shelf tile's menu is the whole editor: four move rows (front / left
/ right / end, reusing the playlist menu's ordering idiom) plus the unpin, over
menu rows rather than drag & drop — dragging inside a horizontal, scrolling
Carousel fights the scroll, and menu rows are keyboard-reachable for free. The
reorder is optimistic on the cached payload and re-asks the server on failure
rather than showing an order that was never accepted.

The exhausted shelf tile (a pinned channel with nothing unwatched left) is
`aria-disabled`, not `disabled`: measured in Chromium, a disabled button still
receives contextmenu and pointerdown, but it loses focus — and with it Shift+F10,
the only keyboard route to the menu it most needs.

Verified end to end in the browser against the live account: all five pin kinds,
the reorder (persisted across a reload), the unpin, and the honest Unpin label on
a resume tile that is already on the shelf.

frontend/src/i18n/locales/en/home.json

@@ -32,6 +32,20 @@
     "unwatchedCount_one": "{{count}} unwatched",
     "unwatchedCount_other": "{{count}} unwatched",
     "itemCount_one": "{{count}} video",
-    "itemCount_other": "{{count}} videos"
+    "itemCount_other": "{{count}} videos",
+    "moveFirst": "To the front",
+    "moveLeft": "Left",
+    "moveRight": "Right",
+    "moveLast": "To the end",
+    "moveFailed": "Could not reorder the shelf."
+  },
+  "pin": {
+    "menu": "Comfort shelf",
+    "add": "Pin to comfort shelf",
+    "remove": "Remove from shelf",
+    "added": "{{title}} is on your comfort shelf.",
+    "removed": "{{title}} is off your comfort shelf.",
+    "addFailed": "Could not pin it to the shelf.",
+    "removeFailed": "Could not remove it from the shelf."
   }
 }

frontend/src/i18n/locales/hu/home.json

@@ -32,6 +32,20 @@
     "unwatchedCount_one": "{{count}} megnézetlen",
     "unwatchedCount_other": "{{count}} megnézetlen",
     "itemCount_one": "{{count}} videó",
-    "itemCount_other": "{{count}} videó"
+    "itemCount_other": "{{count}} videó",
+    "moveFirst": "A polc elejére",
+    "moveLeft": "Balra",
+    "moveRight": "Jobbra",
+    "moveLast": "A polc végére",
+    "moveFailed": "Nem sikerült átrendezni a polcot."
+  },
+  "pin": {
+    "menu": "Komfort polc",
+    "add": "Komfort polcra",
+    "remove": "Levétel a polcról",
+    "added": "{{title}} felkerült a komfort polcra.",
+    "removed": "{{title}} lekerült a komfort polcról.",
+    "addFailed": "Nem sikerült a polcra tűzni.",
+    "removeFailed": "Nem sikerült levenni a polcról."
   }
 }