add settimezone command and timezone display in settings

- New /settimezone <IANA name> command to change user timezone
- Shows current timezone in settings menu
- timezone callback shows current value and instructions
- Updated /help with the new command

internal/bot/handlers.go

@@ -109,6 +109,8 @@ func (h *Handler) HandleMessage(update tgbotapi.Update) {
 		h.handleSetReportTime(msg)
 	case "/setaccent":
 		h.handleAccentMsg(msg)
+	case "/settimezone":
+		h.handleSetTimezone(msg)
 	default:
 		h.sendText(msg.Chat.ID, "Unknown command")
 	}
@@ -154,6 +156,8 @@ func (h *Handler) HandleCallback(update tgbotapi.Update) {
 		h.calTypeCallback(chatID, msgID, cb.ID)
 	case "accent":
 		h.accentCallback(chatID, msgID, cb.ID)
+	case "timezone":
+		h.timezoneCallback(chatID, msgID, cb.ID)
 	case "history":
 		h.historyCallback(chatID, msgID, cb.ID)
 	case "reporttoggle":
@@ -344,6 +348,36 @@ func (h *Handler) handleAccentMsg(msg *tgbotapi.Message) {
 	h.Bot.Send(reply)
 }
 
+func (h *Handler) handleSetTimezone(msg *tgbotapi.Message) {
+	arg := msg.CommandArguments()
+	if arg == "" {
+		user, err := h.getOrCreateUser(msg.Chat.ID)
+		if err != nil {
+			h.sendText(msg.Chat.ID, "Error loading profile")
+			return
+		}
+		h.sendText(msg.Chat.ID, fmt.Sprintf("Current timezone: %s\nUsage: /settimezone <IANA timezone>\nExamples: Asia/Tehran, Europe/London, America/New_York", user.Timezone))
+		return
+	}
+	loc, err := time.LoadLocation(arg)
+	if err != nil {
+		h.sendText(msg.Chat.ID, fmt.Sprintf("Invalid timezone: %s\nUse IANA format, e.g. Asia/Tehran, Europe/London", arg))
+		return
+	}
+	user, err := h.getOrCreateUser(msg.Chat.ID)
+	if err != nil {
+		h.sendText(msg.Chat.ID, "Error loading profile")
+		return
+	}
+	user.Timezone = arg
+	if err := h.DB.UpdateUser(user); err != nil {
+		h.sendText(msg.Chat.ID, "Error saving timezone")
+		return
+	}
+	now := time.Now().In(loc)
+	h.sendText(msg.Chat.ID, fmt.Sprintf("Timezone set to %s (current time: %s)", arg, now.Format("15:04")))
+}
+
 func (h *Handler) handleStart(msg *tgbotapi.Message) {
 	user, err := h.getOrCreateUser(msg.Chat.ID)
 	if err != nil {
@@ -371,6 +405,7 @@ func (h *Handler) handleHelp(msg *tgbotapi.Message) {
 /reporttoggle - Enable/disable auto report
 /setreporttime HH:MM - Set daily report time
 /setaccent - Select accent color
+/settimezone <name> - Set your timezone (e.g. Asia/Tehran)
 
 Buttons on the main menu also work.`
 	h.sendText(msg.Chat.ID, text)
@@ -469,6 +504,9 @@ func (h *Handler) buildSettingsKeyboard(user *db.User) (string, tgbotapi.InlineK
 		reportStatus = "enabled"
 	}
 	var rows [][]tgbotapi.InlineKeyboardButton
+	rows = append(rows, tgbotapi.NewInlineKeyboardRow(
+		tgbotapi.NewInlineKeyboardButtonData(fmt.Sprintf("Timezone: %s", user.Timezone), "timezone"),
+	))
 	rows = append(rows, tgbotapi.NewInlineKeyboardRow(
 		tgbotapi.NewInlineKeyboardButtonData(fmt.Sprintf("Accent: %s", user.ExportAccent), "accent"),
 	))
@@ -502,6 +540,23 @@ func (h *Handler) accentCallback(chatID int64, msgID int, callbackID string) {
 	h.Bot.Send(edit)
 }
 
+func (h *Handler) timezoneCallback(chatID int64, msgID int, callbackID string) {
+	defer h.Bot.Request(tgbotapi.NewCallback(callbackID, ""))
+	user, err := h.getOrCreateUser(chatID)
+	if err != nil {
+		return
+	}
+	text := fmt.Sprintf("Current timezone: %s\n\nUse /settimezone <name> to change it.\nExamples: Asia/Tehran, Europe/London, America/New_York", user.Timezone)
+	kb := tgbotapi.NewInlineKeyboardMarkup(
+		tgbotapi.NewInlineKeyboardRow(
+			tgbotapi.NewInlineKeyboardButtonData("Back to Settings", "back_settings"),
+		),
+	)
+	edit := tgbotapi.NewEditMessageText(chatID, msgID, text)
+	edit.ReplyMarkup = &kb
+	h.Bot.Send(edit)
+}
+
 func (h *Handler) buildAccentKeyboard(user *db.User) (string, tgbotapi.InlineKeyboardMarkup) {
 	accents := []struct {
 		name  string