fix: resolve go vet error and dayStart logic in ComputeDailyTotals

- Fix 'string(d)' int-to-rune conversion in rpg_test.go by using fmt.Sprintf
- Fix ComputeDailyTotals dayStart logic: initial state should be StateWorking
  when dayStart > 0, correctly counting work from dayStart to first out event
- Update README project structure to reflect new domain/handler/repo layout
- Implement missing achievements: rpg_pioneer (on RPG enable) and
  salary_setter (on first rate set)
- Add tryUnlockAchievement helper to Handler

internal/handler/salary.go

@@ -0,0 +1,95 @@
+package handler
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/go-telegram/bot/models"
+
+	"worktimeBot/internal/domain"
+)
+
+// -- Command --
+
+func (h *Handler) handleSalary(ctx context.Context, msg *models.Message, user *domain.User) {
+	text, err := h.buildSalaryEstimate(user)
+	if err != nil {
+		h.sendText(ctx, msg.Chat.ID, err.Error())
+		return
+	}
+	h.sendWithKB(ctx, msg.Chat.ID, text, backKeyboard())
+}
+
+// -- Callback --
+
+func (h *Handler) salaryCallback(ctx context.Context, chatID int64, msgID int, cbID string, user *domain.User) {
+	defer h.answerCb(ctx, cbID)
+	text, err := h.buildSalaryEstimate(user)
+	if err != nil {
+		text = err.Error()
+	}
+	kb := backKeyboard()
+	h.editText(ctx, chatID, msgID, text, &kb)
+}
+
+// -- Builders --
+
+func (h *Handler) buildSalaryEstimate(user *domain.User) (string, error) {
+	st, err := h.Repo.GetOrCreateSettings(user.ID)
+	if err != nil {
+		return "", err
+	}
+	if st.HourlyRate <= 0 {
+		return "No hourly rate configured.\nUse /setrate <amount> to set your rate.", nil
+	}
+	loc := h.loadLocation(user.Timezone)
+	now := time.Now().In(loc)
+	calY, calM := now.Year(), int(now.Month())
+	switch user.Calendar {
+	case "jalali":
+		calY, calM, _ = domain.GregorianToJalali(calY, calM, now.Day())
+	case "hijri":
+		calY, calM, _ = domain.GregorianToHijri(calY, calM, now.Day())
+	}
+	startStr, endStr := domain.MonthGregorianRange(user.Calendar, calY, calM)
+	days, err := h.Repo.GetUserDaysInRange(user.ID, startStr, endStr)
+	if err != nil {
+		return "", err
+	}
+	est := h.computeMonthlySalary(days, user.ID, st.HourlyRate, loc)
+	est.Currency = st.Currency
+	est.HourlyRate = st.HourlyRate
+	title := domain.FormatMonthTitle(user.Calendar, calY, calM)
+	return fmt.Sprintf("Salary estimate for %s\n%s\nRate: %s%.2f/hr\nDays worked: %d\nHours: %.1f",
+		title, est.FormatSalary(st.Currency), domain.CurrencySymbol(st.Currency), st.HourlyRate,
+		est.WorkDays, est.WorkHours), nil
+}
+
+func (h *Handler) computeMonthlySalary(days []domain.Day, userID int64, hourlyRate float64, loc *time.Location) domain.SalaryEstimate {
+	var totalWork int64
+	workDayCount := 0
+	for _, day := range days {
+		if day.IsDayOff {
+			continue
+		}
+		events, err := h.Repo.EventsForDayByDayID(day.ID)
+		if err != nil || len(events) == 0 {
+			continue
+		}
+		y, m, d := domain.ParseGregorianDateKey(day.Date)
+		dayStart := time.Date(y, time.Month(m), d, 0, 0, 0, 0, loc).Unix()
+		dayEnd := time.Date(y, time.Month(m), d, 23, 59, 59, 0, loc).Unix()
+		totals := domain.ComputeDailyTotals(events, day.MinBreakThreshold, dayStart, dayEnd)
+		if totals.TotalSeconds > 0 {
+			totalWork += totals.TotalSeconds
+			workDayCount++
+		}
+	}
+	hours := float64(totalWork) / domain.SecondsPerHour
+	gross := domain.ComputeDailySalary(totalWork, hourlyRate)
+	return domain.SalaryEstimate{
+		WorkSeconds: totalWork, WorkHours: hours,
+		GrossEarning: gross, WorkDays: workDayCount,
+	}
+}