/app/                          # Khu vuc rieng, khong public (chua bi mat + logic)
/app/cau_hinh/
  moi_truong.php               # Bien moi truong (DEV/PROD), ten DB, tz, ...
  co_so_du_lieu.php            # Ket noi PDO
  he_thong.php                 # Doc/ghi bang cau_hinh (bao tri, tieu de, ...)
  duong_dan.php                # Dinh nghia thu muc uploads/json/log

/app/bao_mat/
  link_gas.php                 # CHUA link web app Apps Script (JSON don hang) - bi mat
  khoa_chu.php                 # Khoa/secret noi bo (neu can ky token)
/app/loi/
  xac_thuc.php                 # Auth admin (dang nhap/dang xuat, session)
  bao_tri_guard.php            # Chan truy cap khi bat bao tri
  phan_hoi.php                 # Helpers JSON/HTML response
  tien_ich.php                 # Ham tien ich chung (regex sdt, format, …)

/app/thu_vien/
  xlsx_doc.php                 # Doc XLSX/CSV don gian (khong can Composer)
  json_io.php                  # Ghi/Doc JSON an toan (file -> array -> file)
/app/mo_hinh/
  NguoiDung.php
  CauHinh.php
  TapTin.php
  ExcelPhanVung.php
  ThecbeDong.php
  DonHangCache.php
  NhatKy.php
/app/du_lieu/
  uploads/                     # Noi luu file excel goc (ngoai public)
  json/                        # Noi luu file JSON da xuat de Google Sheet keo
  nhat_ky/                     # Log he thong (neu ghi file)
  tam/                         # File tam thoi

/public_html/
  index.php                    # Trang gioi thieu + o tra cuu (khach hang, khong login)
  dang_nhap.php                # Chi admin moi co (user khong can)
  dang_xuat.php
  404.php

/public_html/api/
  tra_cuu.php                  # API tra cuu theo so dien thoai (doc tu GAS + cache)
  json_file.php                # Cong khai JSON theo file_id + phan vung (cho Google Sheet)
  admin_api.php                # API rieng admin: upload xlsx, tao JSON, bat/tat bao tri, ...

/public_html/quan_tri/
  index.php                    # Tong quan, thong ke
  don_hang.php                 # Quan ly don (xem/loc/refresh cache)
  tep_tai_len.php              # Upload Excel, chon hang tu/den, xuat JSON, lich su
  nhat_ky.php                  # Xem nhat ky tra cuu, hanh dong admin
  cau_hinh.php                 # Cau hinh he thong (link GAS, tieu de site, …)
  bao_tri.php                  # Cong tac bao tri on/off + noi dung thong bao

/tools/
  tao_bang_sql.sql             # File SQL khoi tao DB (ban o duoi)
  huong_dan.txt                # Ghi chu trien khai