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

cmd/bot/main.go

@@ -4,8 +4,11 @@ import (
 	"log/slog"
 	"net/http"
 	"os"
+	"os/signal"
 	"strconv"
 	"strings"
+	"sync"
+	"syscall"
 	"time"
 
 	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
@@ -40,29 +43,62 @@ func main() {
 	}
 
 	allowedUsers := parseAllowedUsers(os.Getenv("BOT_ALLOWED_USERS"))
-
 	handler := bot.NewHandler(botAPI, dbStore, allowedUsers)
 
-	slog.Info("bot started",
-		"bot_user", botAPI.Self.UserName,
-		"allowed_users", len(allowedUsers),
-		"polling", true,
-	)
+	stop := make(chan struct{})
+	var wg sync.WaitGroup
 
-	webhookURL := os.Getenv("BOT_WEBHOOK_URL")
-	if webhookURL != "" {
-		startWebhook(botAPI, handler, webhookURL)
+	if url := os.Getenv("BOT_WEBHOOK_URL"); url != "" {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			startWebhook(botAPI, handler, url)
+		}()
 	} else {
 		if _, err := botAPI.Request(tgbotapi.DeleteWebhookConfig{}); err != nil {
 			slog.Error("delete webhook", "error", err)
 		}
 
-		go dailyReportScheduler(handler, dbStore)
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			dailyReportScheduler(handler, dbStore, stop)
+		}()
 
-		u := tgbotapi.NewUpdate(0)
-		u.Timeout = 30
-		updates := botAPI.GetUpdatesChan(u)
-		for update := range updates {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			startPolling(botAPI, handler, stop)
+		}()
+	}
+
+	slog.Info("bot started",
+		"bot_user", botAPI.Self.UserName,
+		"allowed_users", len(allowedUsers),
+		"mode", map[bool]string{true: "webhook", false: "polling"}[os.Getenv("BOT_WEBHOOK_URL") != ""],
+	)
+
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	s := <-sig
+	slog.Info("shutting down", "signal", s.String())
+	close(stop)
+	wg.Wait()
+	dbStore.Close()
+}
+
+func startPolling(botAPI *tgbotapi.BotAPI, handler *bot.Handler, stop chan struct{}) {
+	u := tgbotapi.NewUpdate(0)
+	u.Timeout = 30
+	updates := botAPI.GetUpdatesChan(u)
+	for {
+		select {
+		case <-stop:
+			return
+		case update, ok := <-updates:
+			if !ok {
+				return
+			}
 			if update.Message != nil {
 				handler.HandleMessage(update)
 			}
@@ -90,7 +126,7 @@ func parseAllowedUsers(raw string) map[int64]bool {
 	return m
 }
 
-func dailyReportScheduler(h *bot.Handler, store *db.Store) {
+func dailyReportScheduler(h *bot.Handler, store *db.Store, stop chan struct{}) {
 	for {
 		now := time.Now()
 		next := time.Date(now.Year(), now.Month(), now.Day(), 23, 0, 0, 0, now.Location())
@@ -98,9 +134,14 @@ func dailyReportScheduler(h *bot.Handler, store *db.Store) {
 			next = next.AddDate(0, 0, 1)
 		}
 		slog.Info("daily report scheduler", "next_run", next)
-		time.Sleep(time.Until(next))
 
-		chatIDStr, err := store.GetSetting("chat_id")
+		select {
+		case <-stop:
+			return
+		case <-time.After(time.Until(next)):
+		}
+
+		chatIDStr, err := store.GetSetting(0, "report_chat_id")
 		if err != nil {
 			slog.Error("daily report: chat_id not found")
 			continue