feat: add MySQL database support alongside SQL Server

This commit implements multi-database support, allowing the system to switch
between SQL Server and MySQL databases seamlessly.

## New Features
- Database type selection (SQL Server or MySQL) via configuration
- Automatic table name conversion between formats ([dbo].[table] → dbo_table)
- Automatic parameter placeholder handling (? for SQL Server, %s for MySQL)
- GUI settings tab now includes database type dropdown and MySQL configuration

## Database Abstraction Layer
- db/base_connection.py: Abstract base class for database connections
- db/sqlserver_connection.py: SQL Server implementation
- db/mysql_connection.py: MySQL implementation using mysql-connector-python
- db/connection_factory.py: Factory pattern for creating connections
- db/table_name_converter.py: Table name format conversion utility

## DAO Base Class
- db/base_dao.py: Base DAO with helper methods for SQL conversion and placeholders

## Updated Components
- config/schema.py: Extended with DatabaseType enum and MySQL/SQLServer config classes
- config/defaults.py: Added MySQL default configuration
- config/loader.py: Updated to handle new database structure
- db/connection.py: Refactored to use factory pattern and load user config
- All DAO files: Updated to inherit from BaseDAO with automatic conversion

## Dependencies
- Added mysql-connector-python>=8.0.0 to requirements.txt

## Configuration
To use MySQL, set db_type to "mysql" in config/user_settings.json:
{
  "database": {
    "db_type": "mysql",
    "mysql": {
      "host": "192.168.31.83",
      "port": 3306,
      "database": "BLD_DB",
      "username": "remote_user",
      "password": "3.1415926Beeke"
    }
  }
}

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

db/bip_users_dao.py

@@ -2,10 +2,12 @@
 BIPUsers DAO - Data access object for user authentication and management
 """
 from typing import Optional, Dict, Any, List
+from db.base_dao import BaseDAO
 from db.connection import get_connection
+from config.schema import DatabaseType
 
 
-class BIPUsersDAO:
+class BIPUsersDAO(BaseDAO):
     """Data access object for BIPUsers table"""
 
     def authenticate(self, username: str, password: str) -> Optional[Dict[str, Any]]:
@@ -20,11 +22,23 @@ class BIPUsersDAO:
             Dict with user info if authentication successful, None otherwise
             Returns: {id, username, user_type}
         """
-        sql = """
-        SELECT [ID], [UserName], [UserType]
-        FROM [dbo].[BIPUsers]
-        WHERE [UserName] = ? AND [Password] = ?
-        """
+        table_name = self._convert_sql('[dbo].[BIPUsers]')
+        placeholder = self._get_placeholder()
+
+        # 根据数据库类型选择列名格式
+        if self._db_type == DatabaseType.MYSQL:
+            sql = f"""
+            SELECT ID, UserName, UserType
+            FROM {table_name}
+            WHERE UserName = {placeholder} AND Password = {placeholder}
+            """
+        else:
+            sql = f"""
+            SELECT [ID], [UserName], [UserType]
+            FROM {table_name}
+            WHERE [UserName] = {placeholder} AND [Password] = {placeholder}
+            """
+
         with get_connection() as db:
             results = db.execute_query(sql, (username, password))
             if results:
@@ -42,11 +56,22 @@ class BIPUsersDAO:
         Returns:
             List of user dictionaries: [{id, username, user_type, create_time}]
         """
-        sql = """
-        SELECT [ID], [UserName], [UserType], [CreateTime]
-        FROM [dbo].[BIPUsers]
-        ORDER BY [UserName]
-        """
+        table_name = self._convert_sql('[dbo].[BIPUsers]')
+
+        # 根据数据库类型选择列名格式
+        if self._db_type == DatabaseType.MYSQL:
+            sql = f"""
+            SELECT ID, UserName, UserType, CreateTime
+            FROM {table_name}
+            ORDER BY UserName
+            """
+        else:
+            sql = f"""
+            SELECT [ID], [UserName], [UserType], [CreateTime]
+            FROM {table_name}
+            ORDER BY [UserName]
+            """
+
         with get_connection() as db:
             results = db.execute_query(sql)
             return [
@@ -71,10 +96,21 @@ class BIPUsersDAO:
         Returns:
             True if successful, False otherwise
         """
-        sql = """
-        INSERT INTO [dbo].[BIPUsers] ([UserName], [Password], [UserType])
-        VALUES (?, ?, ?)
-        """
+        table_name = self._convert_sql('[dbo].[BIPUsers]')
+        placeholder = self._get_placeholder()
+
+        # 根据数据库类型选择列名格式
+        if self._db_type == DatabaseType.MYSQL:
+            sql = f"""
+            INSERT INTO {table_name} (UserName, Password, UserType)
+            VALUES ({placeholder}, {placeholder}, {placeholder})
+            """
+        else:
+            sql = f"""
+            INSERT INTO {table_name} ([UserName], [Password], [UserType])
+            VALUES ({placeholder}, {placeholder}, {placeholder})
+            """
+
         try:
             with get_connection() as db:
                 db.execute_update(sql, (username, password, user_type))
@@ -94,11 +130,23 @@ class BIPUsersDAO:
         Returns:
             True if successful, False otherwise
         """
-        sql = """
-        UPDATE [dbo].[BIPUsers]
-        SET [UserType] = ?
-        WHERE [UserName] = ?
-        """
+        table_name = self._convert_sql('[dbo].[BIPUsers]')
+        placeholder = self._get_placeholder()
+
+        # 根据数据库类型选择列名格式
+        if self._db_type == DatabaseType.MYSQL:
+            sql = f"""
+            UPDATE {table_name}
+            SET UserType = {placeholder}
+            WHERE UserName = {placeholder}
+            """
+        else:
+            sql = f"""
+            UPDATE {table_name}
+            SET [UserType] = {placeholder}
+            WHERE [UserName] = {placeholder}
+            """
+
         try:
             with get_connection() as db:
                 db.execute_update(sql, (user_type, username))
@@ -118,11 +166,23 @@ class BIPUsersDAO:
         Returns:
             True if successful, False otherwise
         """
-        sql = """
-        UPDATE [dbo].[BIPUsers]
-        SET [Password] = ?
-        WHERE [UserName] = ?
-        """
+        table_name = self._convert_sql('[dbo].[BIPUsers]')
+        placeholder = self._get_placeholder()
+
+        # 根据数据库类型选择列名格式
+        if self._db_type == DatabaseType.MYSQL:
+            sql = f"""
+            UPDATE {table_name}
+            SET Password = {placeholder}
+            WHERE UserName = {placeholder}
+            """
+        else:
+            sql = f"""
+            UPDATE {table_name}
+            SET [Password] = {placeholder}
+            WHERE [UserName] = {placeholder}
+            """
+
         try:
             with get_connection() as db:
                 db.execute_update(sql, (new_password, username))
@@ -141,10 +201,21 @@ class BIPUsersDAO:
         Returns:
             True if successful, False otherwise
         """
-        sql = """
-        DELETE FROM [dbo].[BIPUsers]
-        WHERE [UserName] = ?
-        """
+        table_name = self._convert_sql('[dbo].[BIPUsers]')
+        placeholder = self._get_placeholder()
+
+        # 根据数据库类型选择列名格式
+        if self._db_type == DatabaseType.MYSQL:
+            sql = f"""
+            DELETE FROM {table_name}
+            WHERE UserName = {placeholder}
+            """
+        else:
+            sql = f"""
+            DELETE FROM {table_name}
+            WHERE [UserName] = {placeholder}
+            """
+
         try:
             with get_connection() as db:
                 db.execute_update(sql, (username,))
@@ -163,10 +234,21 @@ class BIPUsersDAO:
         Returns:
             True if username exists, False otherwise
         """
-        sql = """
-        SELECT COUNT(*) as count FROM [dbo].[BIPUsers]
-        WHERE [UserName] = ?
-        """
+        table_name = self._convert_sql('[dbo].[BIPUsers]')
+        placeholder = self._get_placeholder()
+
+        # 根据数据库类型选择列名格式
+        if self._db_type == DatabaseType.MYSQL:
+            sql = f"""
+            SELECT COUNT(*) as count FROM {table_name}
+            WHERE UserName = {placeholder}
+            """
+        else:
+            sql = f"""
+            SELECT COUNT(*) as count FROM {table_name}
+            WHERE [UserName] = {placeholder}
+            """
+
         with get_connection() as db:
             results = db.execute_query(sql, (username,))
             return results[0]['count'] > 0 if results else False