feat: implement user authentication and permission-based data filtering

Add user login system with role-based access control:
- Admin users see all data and can filter by any manager
- Regular users only see records where ManagerName matches their username

New components:
- BIPUsersDAO: user authentication and management
- SessionManager: singleton session state management
- LoginDialog: modal login UI for app startup
- init_users.sql: initial user setup script

Permission enforcement:
- Material validation tab: hide manager filter for non-admin, force filter by current user
- Material type management: hide filter UI for non-admin, filter at database level
- Window title and status bar display current user info

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

gui/login_dialog.py

@@ -0,0 +1,162 @@
+"""
+Login Dialog - Modal dialog for user authentication
+"""
+import tkinter as tk
+from tkinter import ttk, messagebox
+from typing import Optional, Tuple
+
+
+class LoginDialog:
+    """
+    Modal login dialog that captures user credentials
+
+    Usage:
+        login_dialog = LoginDialog(parent)
+        credentials = login_dialog.get_credentials()
+        if credentials:
+            username, password = credentials
+            # Proceed with authentication
+    """
+
+    def __init__(self, parent):
+        """
+        Initialize the login dialog
+
+        Args:
+            parent: The parent Tkinter window
+        """
+        self.parent = parent
+        self.result = None  # Will hold (username, password) or None
+        self.dialog = None
+
+        # Create dialog as modal
+        self._create_dialog()
+        self.parent.wait_window(self.dialog)
+
+    def _create_dialog(self):
+        """Create the login dialog UI"""
+        self.dialog = tk.Toplevel(self.parent)
+        self.dialog.title("ERP 自动化工具 - 登录")
+        self.dialog.geometry("400x250")
+        self.dialog.resizable(False, False)
+
+        # Center the dialog on parent
+        self.dialog.transient(self.parent)
+        self.dialog.grab_set()
+
+        # Calculate position to center on parent
+        self.parent.update_idletasks()
+        parent_x = self.parent.winfo_x()
+        parent_y = self.parent.winfo_y()
+        parent_width = self.parent.winfo_width()
+        parent_height = self.parent.winfo_height()
+
+        dialog_width = 400
+        dialog_height = 250
+        x = parent_x + (parent_width - dialog_width) // 2
+        y = parent_y + (parent_height - dialog_height) // 2
+        self.dialog.geometry(f"{dialog_width}x{dialog_height}+{x}+{y}")
+
+        # Create UI elements
+        self._create_widgets()
+
+        # Bind Enter key to login button
+        self.dialog.bind('<Return>', lambda e: self._on_login())
+
+        # Focus on username entry
+        self.username_entry.focus_set()
+
+    def _create_widgets(self):
+        """Create the dialog widgets"""
+        # Main frame with padding
+        main_frame = ttk.Frame(self.dialog, padding="20")
+        main_frame.pack(fill=tk.BOTH, expand=True)
+
+        # Title
+        title_label = ttk.Label(
+            main_frame,
+            text="请登录",
+            font=('', 16, 'bold')
+        )
+        title_label.pack(pady=(0, 20))
+
+        # Username field
+        username_frame = ttk.Frame(main_frame)
+        username_frame.pack(fill=tk.X, pady=5)
+
+        ttk.Label(username_frame, text="用户名:", width=10).pack(side=tk.LEFT)
+        self.username_entry = ttk.Entry(username_frame)
+        self.username_entry.pack(side=tk.LEFT, fill=tk.X, expand=True)
+
+        # Password field
+        password_frame = ttk.Frame(main_frame)
+        password_frame.pack(fill=tk.X, pady=5)
+
+        ttk.Label(password_frame, text="密码:", width=10).pack(side=tk.LEFT)
+        self.password_entry = ttk.Entry(password_frame, show="*")
+        self.password_entry.pack(side=tk.LEFT, fill=tk.X, expand=True)
+
+        # Buttons frame
+        button_frame = ttk.Frame(main_frame)
+        button_frame.pack(pady=(20, 0))
+
+        # Login button
+        login_btn = ttk.Button(
+            button_frame,
+            text="登录",
+            command=self._on_login,
+            width=10
+        )
+        login_btn.pack(side=tk.LEFT, padx=5)
+
+        # Cancel button
+        cancel_btn = ttk.Button(
+            button_frame,
+            text="取消",
+            command=self._on_cancel,
+            width=10
+        )
+        cancel_btn.pack(side=tk.LEFT, padx=5)
+
+        # Version info
+        version_label = ttk.Label(
+            main_frame,
+            text="v1.0",
+            font=('', 8),
+            foreground='gray'
+        )
+        version_label.pack(side=tk.BOTTOM, pady=10)
+
+    def _on_login(self):
+        """Handle login button click"""
+        username = self.username_entry.get().strip()
+        password = self.password_entry.get().strip()
+
+        if not username:
+            messagebox.showwarning("输入错误", "请输入用户名")
+            self.username_entry.focus_set()
+            return
+
+        if not password:
+            messagebox.showwarning("输入错误", "请输入密码")
+            self.password_entry.focus_set()
+            return
+
+        # Return credentials for validation
+        self.result = (username, password)
+        self.dialog.destroy()
+
+    def _on_cancel(self):
+        """Handle cancel button click"""
+        self.result = None
+        self.dialog.destroy()
+
+    def get_credentials(self) -> Optional[Tuple[str, str]]:
+        """
+        Get the entered credentials
+
+        Returns:
+            Tuple of (username, password) if user clicked Login,
+            None if user clicked Cancel or closed the dialog
+        """
+        return self.result