feat: add channel edit in admin, hide subscribed channels in blocking screen

- Admin panel: added Edit button on channel cards with inline edit form
  (title, link, sort order) using existing PATCH API
- Subscription screen: filter out already-subscribed channels so users
  only see what they still need to subscribe to
- Updated channelIdHint to remove @username reference (numeric only)
- Added i18n keys: edit, editing, form.save (en/ru/fa/zh)

src/locales/fa.json

@@ -1011,16 +1011,19 @@
       "disabled": "غیرفعال",
       "enable": "فعال‌سازی",
       "disable": "غیرفعال‌سازی",
+      "edit": "ویرایش",
+      "editing": "ویرایش",
       "delete": "حذف",
       "deleteConfirm": "این کانال حذف شود؟",
       "sortOrder": "ترتیب",
       "form": {
         "title": "نام نمایشی",
         "channelId": "شناسه کانال",
-        "channelIdHint": "@username یا -100XXXXXXXXXX",
+        "channelIdHint": "-100XXXXXXXXXX",
         "channelLink": "لینک کانال",
         "channelLinkHint": "https://t.me/channel",
         "submit": "افزودن",
+        "save": "ذخیره",
         "cancel": "لغو"
       }
     },