feat: multi-user isolation and graceful shutdown

- Add chat_id to events, settings, and days_off for per-user data
- Add proper graceful shutdown (signal handling, WaitGroup)
- Separate polling and webhook modes with goroutine management
- Add schema migration from single-user to multi-user schema
- Refactor handlers with shared actionFunc pattern (msg + callback)
- Fix schema path for Docker deployment (/app/db/schema.sql)
- Remove emoji from output text for cleaner formatting

internal/bot/export.go

@@ -9,7 +9,7 @@ import (
 	"worktimeBot/internal/db"
 )
 
-func GenerateMonthlyReport(store *db.Store, year int, month time.Month) ([]byte, error) {
+func GenerateMonthlyReport(store *db.Store, chatID int64, year int, month time.Month) ([]byte, error) {
 	f := excelize.NewFile()
 	defer f.Close()
 
@@ -59,7 +59,6 @@ func GenerateMonthlyReport(store *db.Store, year int, month time.Month) ([]byte,
 	})
 
 	monthName := time.Date(year, month, 1, 0, 0, 0, 0, time.UTC).Format("January 2006")
-
 	f.SetCellValue(sheet, "A1", fmt.Sprintf("Work Time Report — %s", monthName))
 	f.MergeCell(sheet, "A1", "E1")
 	f.SetCellStyle(sheet, "A1", "E1", titleStyle)
@@ -89,7 +88,7 @@ func GenerateMonthlyReport(store *db.Store, year int, month time.Month) ([]byte,
 	for d := firstDay; !d.After(lastDay); d = d.AddDate(0, 0, 1) {
 		dateStr := d.Format("2006-01-02")
 
-		isOff, err := store.IsDayOff(dateStr)
+		isOff, err := store.IsDayOff(chatID, dateStr)
 		if err != nil {
 			return nil, err
 		}
@@ -97,7 +96,7 @@ func GenerateMonthlyReport(store *db.Store, year int, month time.Month) ([]byte,
 			continue
 		}
 
-		events, err := store.EventsForDay(dateStr)
+		events, err := store.EventsForDay(chatID, dateStr)
 		if err != nil {
 			return nil, err
 		}