feat(auth): implement web login endpoint with JWT

internal/api/auth_handler.go

@@ -78,3 +78,31 @@ func (h *AuthHandler) Join(w http.ResponseWriter, r *http.Request) {
 	// В случае успеха возвращаем пустой ответ со статусом 204
 	w.WriteHeader(http.StatusNoContent)
 }
+
+func (h *AuthHandler) Login(w http.ResponseWriter, r *http.Request) {
+	var req models.LoginRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, "Invalid request body", http.StatusBadRequest)
+		return
+	}
+
+	token, user, err := h.Service.LoginUser(r.Context(), req)
+	if err != nil {
+		if errors.Is(err, core.ErrInvalidCredentials) {
+			http.Error(w, "Invalid username or password", http.StatusUnauthorized)
+			return
+		}
+		log.Printf("internal server error during login: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	response := models.LoginResponse{
+		Token: token,
+		User:  user,
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	json.NewEncoder(w).Encode(response)
+}