feat: 项目重命名 SQL-Platform + 数据源表单重写(连接模式/流程/排除DB/脱敏)

- 项目名称 Web-Lite Pro → SQL-Platform 全局替换(13处)
- Instance 模型新增: access_mode, workflow, excluded_databases, mask_fields
- 创建数据源表单: 分区卡片(数据源信息/连接模式/流程/高级配置)
- 后端 JSON 字段序列化/反序列化
- 新增 5 个 Instance 字段测试 (133 total)

backend/app/models/instance.py

@@ -18,5 +18,12 @@ class Instance(Base):
     description = Column(Text, nullable=True)
     status = Column(String(20), default="disconnected")  # connected / disconnected / error
     version = Column(String(50), nullable=True)
+
+    # 新增字段
+    access_mode = Column(String(20), default="readwrite")  # readwrite / read / write
+    workflow = Column(Text, nullable=True)  # JSON: [{stage, role, assignee}]
+    excluded_databases = Column(Text, nullable=True)  # JSON: ["sys", "information_schema", ...]
+    mask_fields = Column(Text, nullable=True)  # JSON: [{table, field, rule}]
+
     created_at = Column(DateTime, server_default=func.now())
     updated_at = Column(DateTime, server_default=func.now(), onupdate=func.now())