feat(feedback): show the sender's interface language and connector bot in admin

In the console feedback detail, show the sender's interface language (account
preferred_language) always, and — for a message that arrived through an external
connector (currently Telegram) — the bot they last used (en/ru, from the
account's service_language).

backend/internal/adminconsole/views.go

@@ -404,21 +404,26 @@ type FeedbackRow struct {
 // user-controlled and rendered as plain auto-escaped text. IsImage gates the inline
 // <img> preview; Banned shows whether the sender already holds the feedback ban.
 type FeedbackDetailView struct {
-	ID             string
-	AccountID      string
-	SenderName     string
-	Source         string
-	Channel        string
-	IP             string
-	Body           string
-	HasAttachment  bool
-	AttachmentName string
-	IsImage        bool
-	Read           bool
-	Archived       bool
-	Replied        bool
-	ReplyBody      string
-	RepliedAt      string
-	CreatedAt      string
-	Banned         bool
+	ID         string
+	AccountID  string
+	SenderName string
+	Source     string
+	Channel    string
+	// InterfaceLanguage is the sender's interface language (account preference);
+	// BotLanguage is the connector bot they last used (en/ru), set only for a
+	// message that arrived through an external connector (Telegram).
+	InterfaceLanguage string
+	BotLanguage       string
+	IP                string
+	Body              string
+	HasAttachment     bool
+	AttachmentName    string
+	IsImage           bool
+	Read              bool
+	Archived          bool
+	Replied           bool
+	ReplyBody         string
+	RepliedAt         string
+	CreatedAt         string
+	Banned            bool
 }