refactor: export full Gregorian range, add timezone fallback, cleanup rate limit, configurable schema path

- GenerateMonthlyReport now takes explicit Gregorian start/end range,
  computed via monthGregorianRange, so Jalali/Hijri months spanning
  two Gregorian months are fully covered in exports.
- Added loadLocation helper (UTC fallback on error) and replaced all
  11 ignored-error call sites in handlers + export.
- Added periodicCleanup goroutine in NewHandler to prevent unbounded
  growth of the rateLimit map.
- schemaPath is now read from SCHEMA_PATH env var (init), defaulting
  to /app/db/schema.sql.
- Migrated sendDayView to use sendOrEdit helper, removing duplicated
  send/edit branching.
- Removed dead code: userYearMonthToGregorian (unused), the old
  startOffset function (replaced).
- Updated README with calendar docs, new env vars, full project tree.
- Updated .env.example and docker-compose.yml with SCHEMA_PATH.
- Simplified Makefile: added fmt, tidy, check, run-dev targets;
  removed broken Make-glob prerequisite pattern.

internal/bot/export.go

@@ -22,7 +22,7 @@ var themes = map[string]themeColors{
 	"catppuccin": {headerFill: "B48DED", border: "D9D0E8", totalFill: "F0E8FC"},
 }
 
-func GenerateMonthlyReport(store *db.Store, userID int64, timezone, accent, calendar string, year int, month time.Month) ([]byte, error) {
+func GenerateMonthlyReport(store *db.Store, userID int64, timezone, accent, calendar string, calYear, calMonth int, start, end time.Time) ([]byte, error) {
 	theme, ok := themes[accent]
 	if !ok {
 		theme = themes["ocean"]
@@ -76,16 +76,7 @@ func GenerateMonthlyReport(store *db.Store, userID int64, timezone, accent, cale
 		Alignment: &excelize.Alignment{Horizontal: "center", Vertical: "center"},
 	})
 
-	var jy, jm int
-	switch calendar {
-	case "jalali":
-		jy, jm, _ = gregorianToJalali(year, int(month), 1)
-	case "hijri":
-		jy, jm, _ = gregorianToHijri(year, int(month), 1)
-	default:
-		jy, jm = year, int(month)
-	}
-	monthName := formatMonthTitle(calendar, jy, jm)
+	monthName := formatMonthTitle(calendar, calYear, calMonth)
 	f.SetCellValue(sheet, "A1", fmt.Sprintf("Work Time Report - %s", monthName))
 	f.MergeCell(sheet, "A1", "F1")
 	f.SetCellStyle(sheet, "A1", "F1", titleStyle)
@@ -106,16 +97,11 @@ func GenerateMonthlyReport(store *db.Store, userID int64, timezone, accent, cale
 	f.SetColWidth(sheet, "E", "E", 10)
 	f.SetColWidth(sheet, "F", "F", 10)
 
-	loc, err := time.LoadLocation(timezone)
-	if err != nil {
-		loc = time.UTC
-	}
+	loc := loadLocation(timezone)
 
 	row := 3
-	firstDay := time.Date(year, month, 1, 0, 0, 0, 0, loc)
-	lastDay := firstDay.AddDate(0, 1, -1)
 
-	userDays, err := store.GetUserDaysInRange(userID, firstDay.Format("2006-01-02"), lastDay.Format("2006-01-02"))
+	userDays, err := store.GetUserDaysInRange(userID, start.Format("2006-01-02"), end.Format("2006-01-02"))
 	if err != nil {
 		return nil, err
 	}
@@ -127,7 +113,7 @@ func GenerateMonthlyReport(store *db.Store, userID int64, timezone, accent, cale
 
 	var totalWork, totalBreak int64
 
-	for d := firstDay; !d.After(lastDay); d = d.AddDate(0, 0, 1) {
+	for d := start; !d.After(end); d = d.AddDate(0, 0, 1) {
 		dateStr := d.Format("2006-01-02")
 		displayDate := formatDateForCalendar(dateStr, calendar)