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/en.json

@@ -1308,16 +1308,19 @@
       "disabled": "Disabled",
       "enable": "Enable",
       "disable": "Disable",
+      "edit": "Edit",
+      "editing": "Editing",
       "delete": "Delete",
       "deleteConfirm": "Delete this channel?",
       "sortOrder": "Order",
       "form": {
         "title": "Display Name",
         "channelId": "Channel ID",
-        "channelIdHint": "@username or -100XXXXXXXXXX",
+        "channelIdHint": "-100XXXXXXXXXX",
         "channelLink": "Channel Link",
         "channelLinkHint": "https://t.me/channel",
         "submit": "Add",
+        "save": "Save",
         "cancel": "Cancel"
       }
     },

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"
       }
     },

src/locales/ru.json

@@ -1334,16 +1334,19 @@
       "disabled": "Отключён",
       "enable": "Включить",
       "disable": "Отключить",
+      "edit": "Изменить",
+      "editing": "Редактирование",
       "delete": "Удалить",
       "deleteConfirm": "Удалить этот канал?",
       "sortOrder": "Порядок",
       "form": {
         "title": "Название",
         "channelId": "ID канала",
-        "channelIdHint": "@username или -100XXXXXXXXXX",
+        "channelIdHint": "-100XXXXXXXXXX",
         "channelLink": "Ссылка на канал",
         "channelLinkHint": "https://t.me/channel",
         "submit": "Добавить",
+        "save": "Сохранить",
         "cancel": "Отмена"
       }
     },

src/locales/zh.json

@@ -1063,16 +1063,19 @@
       "disabled": "已禁用",
       "enable": "启用",
       "disable": "禁用",
+      "edit": "编辑",
+      "editing": "编辑",
       "delete": "删除",
       "deleteConfirm": "删除此频道？",
       "sortOrder": "排序",
       "form": {
         "title": "显示名称",
         "channelId": "频道ID",
-        "channelIdHint": "@username 或 -100XXXXXXXXXX",
+        "channelIdHint": "-100XXXXXXXXXX",
         "channelLink": "频道链接",
         "channelLinkHint": "https://t.me/channel",
         "submit": "添加",
+        "save": "保存",
         "cancel": "取消"
       }
     },