feat(design): the channel menu's Tags and Priority submenus (C1, E28 S3e3b)

Tags A-Z as in-place checks (the menu stays open for the next); Priority
as the fixed steps 10 5 3 2 1 0, an off-scale current value ticked in its
place. A pick re-sorts the list at once, moving only that row
(placeByPriority, the server's order), and the table / card pager and
the focus follow it (DataTable and useCardPager take a reveal seq,
listNav.focusNavItem lands on the row's own "…", a virtualized card
revealed first). ActionMenu rows take check: many | one. The menu reads
the row fresh from the cache and keys its target by id.

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

@@ -118,7 +118,9 @@
     "unsubscribeHint": "Unsubscribe from this channel on YouTube (changes your real account). Read-only mode hides this — use Hide instead.",
     "unsubscribeOnYoutube": "Unsubscribe on YouTube",
     "thisChannel": "This channel",
-    "menu": "Channel actions"
+    "menu": "Channel actions",
+    "priority": "Priority",
+    "noTagsYet": "No tags yet — make one with a row’s tag “+”"
   },
   "notify": {
     "synced": "Synced {{count}} subscriptions",

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

@@ -118,7 +118,9 @@
     "unsubscribeHint": "Leiratkozás erről a csatornáról a YouTube-on (megváltoztatja a valódi fiókodat). Csak olvasható módban ez rejtve van — használd helyette az Elrejtést.",
     "unsubscribeOnYoutube": "Leiratkozás a YouTube-on",
     "thisChannel": "Ez a csatorna",
-    "menu": "Csatorna műveletei"
+    "menu": "Csatorna műveletei",
+    "priority": "Prioritás",
+    "noTagsYet": "Még nincs címkéd — egy sor címke-„+” gombjával hozhatsz létre"
   },
   "notify": {
     "synced": "{{count}} feliratkozás szinkronizálva",