Add JWT authentication

- Create register and login use cases
- Implement JWT service for token generation and validation
- Add authentication middleware to protect habit endpoints
- Create auth HTTP handlers (register, login)
- Update habit handlers to extract userID from JWT token
- Register/login endpoints: POST /auth/register, POST /auth/login
- Habit endpoints now require Bearer token in Authorization header
- Tested: register -> create habit -> list habits works correctly

cmd/api/main.go

@@ -4,9 +4,12 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"strconv"
+	"strings"
 
 	"habit-tracker-api/internal/application/commands"
 	"habit-tracker-api/internal/application/queries"
+	"habit-tracker-api/internal/infrastructure/auth"
 	"habit-tracker-api/internal/infrastructure/config"
 	httpInfra "habit-tracker-api/internal/infrastructure/http"
 	"habit-tracker-api/internal/infrastructure/persistence/sqlite"
@@ -24,16 +27,27 @@ func main() {
 	}
 	defer db.Close()
 
+	jwtExpiryHours, err := parseJWTExpiry(cfg.JWTExpiry)
+	if err != nil {
+		log.Fatalf("Invalid JWT_EXPIRY: %v", err)
+	}
+
+	jwtService := auth.NewJWTService(cfg.JWTSecret, jwtExpiryHours)
+
+	userRepo := sqlite.NewUserRepository(db.Conn())
 	habitRepo := sqlite.NewHabitRepository(db.Conn())
 	entryRepo := sqlite.NewHabitEntryRepository(db.Conn())
 
+	registerHandler := commands.NewRegisterUserHandler(userRepo)
+	loginHandler := queries.NewLoginUserHandler(userRepo)
 	createHandler := commands.NewCreateHabitHandler(habitRepo)
 	getTodaysHandler := queries.NewGetTodaysHabitsHandler(habitRepo, entryRepo)
 	markHandler := commands.NewMarkHabitHandler(entryRepo, habitRepo)
 
+	authHandlers := httpInfra.NewAuthHandlers(registerHandler, loginHandler, jwtService)
 	habitHandlers := httpInfra.NewHabitHandlers(createHandler, getTodaysHandler, markHandler)
 
-	router := httpInfra.NewRouter(cfg.CORSOrigins, habitHandlers)
+	router := httpInfra.NewRouter(cfg.CORSOrigins, habitHandlers, authHandlers, jwtService)
 
 	addr := fmt.Sprintf("%s:%s", cfg.Host, cfg.Port)
 	log.Printf("Server starting on %s", addr)
@@ -42,3 +56,12 @@ func main() {
 		log.Fatalf("Server failed: %v", err)
 	}
 }
+
+func parseJWTExpiry(expiry string) (int, error) {
+	expiry = strings.TrimSpace(expiry)
+	if strings.HasSuffix(expiry, "h") {
+		hours := strings.TrimSuffix(expiry, "h")
+		return strconv.Atoi(hours)
+	}
+	return 0, fmt.Errorf("invalid format, expected format like '24h'")
+}