feat(channels): R14 zoom-fit table — fluid columns + column fogyókúra

- DataTable: opt-in `fixedLayout` (colgroup + table-layout:fixed) so the
  table fits its container at any zoom/text-size; only the channel manager
  opts in — playlists/discovery/Plex keep auto-sizing.
- Remove the N/S/L and Sync columns from the manager table. Fully-synced
  status becomes a ✓ charm on the Stored count; the sync filter moves to an
  `applySyncFilter` pre-filter still driven by the top chips.
- Channel column is now fluid: ChannelLink truncates with the full name on
  hover (title). Data columns get fixed widths so only Channel/About flex.
- N/S/L (normal/short/live) breakdown moves to the channel page: add the
  three counts to the channelDetail endpoint (one grouped query, same
  filters as the list) + the ChannelDetail type + a meta-line entry.
- Drop the now-dead sync/types i18n keys (en+hu).

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

@@ -12,6 +12,7 @@
   "videoCount_other": "{{count}} videos",
   "videoCountStored": "{{stored}} / {{total}} videos",
   "totalViews": "{{formatted}} views",
+  "videoTypes": "{{normal}} normal / {{short}} shorts / {{live}} live",
   "joined": "Joined {{date}}",
   "loadingVideos": "Loading this channel's videos…",
   "tabVideos": "Videos",

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

@@ -68,9 +68,6 @@
     "subs": "Subscribers",
     "lastUpload": "Last upload",
     "length": "Length",
-    "types": "N/S/L",
-    "typesHint": "Videos by type: Normal / Shorts / Live",
-    "sync": "Sync",
     "tags": "Tags",
     "actions": "Actions"
   },
@@ -97,20 +94,13 @@
     "raisePriority": "Raise priority",
     "lowerPriority": "Lower priority",
     "editPriority": "Click to type a priority (negatives allowed)",
-    "recent": "recent",
-    "recentSyncedHint": "Recent uploads synced.",
-    "recentNotSyncedHint": "Recent uploads not fetched yet.",
-    "full": "full",
     "fullHint": "Full history fetched.",
-    "fullNotFetchedHint": "Full back-catalog not fetched yet — use the backfill action in the Actions column.",
     "fullySynced": "fully synced",
     "fullySyncedHint": "Recent uploads and the full back-catalog are both in.",
     "backfillThis": "Backfill this channel",
     "backfillThisHint": "Fetch this channel's full back-catalog (older videos + complete search). Click again to cancel the request.",
     "resetBackfill": "Reset & re-fetch this channel",
     "resetHint": "Admin: re-fetch this channel from scratch (recent + full back-catalog), regardless of its current sync state.",
-    "fullHistoryQueued": "queued",
-    "fullHistoryComing": "coming",
     "queuedRequestedHint": "Full history requested — this channel's whole back-catalog will backfill as the shared quota allows. Click to cancel your request.",
     "queuedByOtherHint": "Another subscriber already requested this channel's full history, so its whole back-catalog is on its way to everyone — nothing to do here.",
     "hiddenHint": "Hidden — this channel's videos are kept out of your feed. Click to show them again.",