refactor: break up large functions, add RPG/league/salary/burnout, fix bugs, add tests

- Refactor GenerateMonthlyReport (198→70), HandleCallback (128→85),
  handleHistoryCallback (131→38), handleExportCallback (100→25),
  checkAchievements (86→25) into extracted helper functions
- Add RPG system (XP, levels, streak, achievements, burnout)
- Add WorkTime League leaderboard
- Add salary estimation with configurable currency/rate
- Add input sanitization (SanitizeNote, SanitizeDisplayName)
- Add settings select-style pickers for toggles (report, RPG, league)
- Add break threshold inline picker UI
- Add event notes with pending state and /note command
- Add multi-calendar support (Jalali, Hijri)
- Add Excel export with theme picker
- Fix: getTodayBreakThreshold uses user's timezone (was UTC)
- Fix: acknowledgeCallback passes real callback ID
- Fix: currency symbol safety with currencySymbol() helper
- Fix: count work hours in summary on day-off days
- Fix: unsilence all error returns from SQL Exec/Bot API/migrations
- Remove stale db/schema.sql and unreferenced computeWeekTotals
- Extract constants: DateLayout, TimeLayout, secondsPerHour, etc.
- Add 12 new tests (XP, salary, sanitize, currency, dateutil)
- Remove duplicate package doc comment in totals.go

internal/bot/league.go

@@ -0,0 +1,157 @@
+package bot
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/go-telegram/bot/models"
+)
+
+// LeagueSortOption represents a valid league sort column.
+type LeagueSortOption string
+
+const (
+	LeagueSortXP     LeagueSortOption = "xp"
+	LeagueSortLevel  LeagueSortOption = "level"
+	LeagueSortStreak LeagueSortOption = "streak"
+	LeagueSortHours  LeagueSortOption = "hours"
+)
+
+// buildLeagueText returns the formatted league rankings.
+func (h *Handler) buildLeagueText(orderBy LeagueSortOption) string {
+	entries, err := h.DB.GetLeagueRankings(string(orderBy))
+	if err != nil {
+		return "League rankings unavailable."
+	}
+	if len(entries) == 0 {
+		return "No participants in the league yet.\nEnable League participation in Settings to join!"
+	}
+
+	var b strings.Builder
+	orderLabel := map[string]string{
+		"xp":     "XP",
+		"level":  "Level",
+		"streak": "Streak",
+		"hours":  "Total Hours",
+	}
+	b.WriteString(fmt.Sprintf("WorkTime League — sorted by %s\n\n", orderLabel[string(orderBy)]))
+
+	// Determine column widths
+	maxUserLen := 0
+	for _, e := range entries {
+		l := len(e.Username)
+		if l > maxUserLen {
+			maxUserLen = l
+		}
+	}
+	if maxUserLen < 8 {
+		maxUserLen = 8
+	}
+	if maxUserLen > 20 {
+		maxUserLen = 20
+	}
+
+	header := fmt.Sprintf("%-3s %-*s %8s %6s %6s %12s", "#", maxUserLen, "Username", "XP", "Level", "Streak", "Hours")
+	b.WriteString(header + "\n")
+	b.WriteString(strings.Repeat("-", len(header)) + "\n")
+
+	for i, e := range entries {
+		rank := i + 1
+		name := e.Username
+		if len(name) > maxUserLen {
+			name = name[:maxUserLen]
+		}
+		b.WriteString(fmt.Sprintf("%-3d %-*s %8d %6d %6d %12.1f\n",
+			rank, maxUserLen, name, e.XP, e.Level, e.Streak, e.TotalHours))
+	}
+
+	b.WriteString(fmt.Sprintf("\n%d participant(s)\n", len(entries)))
+
+	return b.String()
+}
+
+// buildLeagueRankText returns the user's personal rank in the league.
+func (h *Handler) buildLeagueRankText(userID int64) string {
+	entries, err := h.DB.GetLeagueRankings("xp")
+	if err != nil || len(entries) == 0 {
+		return ""
+	}
+
+	for i, e := range entries {
+		if e.UserID == userID {
+			return fmt.Sprintf("League rank: #%d of %d", i+1, len(entries))
+		}
+	}
+	return ""
+}
+
+// handleLeagueMsg handles the /league command.
+func (h *Handler) handleLeagueMsg(ctx context.Context, msg *models.Message) {
+	user, err := h.getOrCreateUser(msg.Chat.ID)
+	if err != nil {
+		h.sendText(ctx, msg.Chat.ID, "Error loading profile")
+		return
+	}
+	st, err := h.DB.GetOrCreateSettings(user.ID)
+	if err != nil {
+		h.sendText(ctx, msg.Chat.ID, "Error loading settings")
+		return
+	}
+	if !st.LeagueOptIn {
+		h.sendText(ctx, msg.Chat.ID, "League participation is disabled.\nEnable it in Settings or use /leaguetoggle.")
+		return
+	}
+	text := h.buildLeagueText(LeagueSortXP)
+	kb := h.buildLeagueKeyboard("xp")
+	h.sendWithKB(ctx, msg.Chat.ID, text, kb)
+}
+
+// handleLeagueCallback handles league inline view.
+func (h *Handler) handleLeagueCallback(ctx context.Context, chatID int64, msgID int, callbackID, orderBy string) {
+	defer h.answerCb(ctx, callbackID)
+	user, err := h.getOrCreateUser(chatID)
+	if err != nil {
+		return
+	}
+	st, err := h.DB.GetOrCreateSettings(user.ID)
+	if err != nil {
+		return
+	}
+	if !st.LeagueOptIn {
+		kb := backKeyboard()
+		h.editText(ctx, chatID, msgID, "League participation is disabled.\nEnable it in Settings to view rankings.", &kb)
+		return
+	}
+	text := h.buildLeagueText(LeagueSortOption(orderBy))
+	kb := h.buildLeagueKeyboard(orderBy)
+	h.editText(ctx, chatID, msgID, text, &kb)
+}
+
+// buildLeagueKeyboard creates the league navigation keyboard.
+func (h *Handler) buildLeagueKeyboard(currentOrder string) models.InlineKeyboardMarkup {
+	orders := []struct {
+		label string
+		data  string
+	}{
+		{"XP", "league_xp"},
+		{"Level", "league_level"},
+		{"Streak", "league_streak"},
+		{"Hours", "league_hours"},
+	}
+
+	rows := [][]models.InlineKeyboardButton{}
+	for _, o := range orders {
+		label := o.label
+		if o.data == "league_"+currentOrder {
+			label = "> " + label
+		}
+		rows = append(rows, []models.InlineKeyboardButton{
+			{Text: label, CallbackData: o.data},
+		})
+	}
+	rows = append(rows, []models.InlineKeyboardButton{
+		{Text: "Back to Menu", CallbackData: "back_menu"},
+	})
+	return models.InlineKeyboardMarkup{InlineKeyboard: rows}
+}