feat(workflow): add database CRUD workflow nodes

[xpert-ai-dev]

Summary

This PR implements database CRUD workflow nodes for the Xpert workflow system, addressing GitHub issue #218.

Changes

1. Updated Interfaces (packages/contracts/src/ai/xpert-table.model.ts)

• Added TDBWhereCondition type for WHERE clause conditions
• Added TDBOrderBy type for ORDER BY clauses
• Enhanced IWFNDBUpdate with where?: TDBWhereCondition[]
• Enhanced IWFNDBDelete with where?: TDBWhereCondition[]
• Enhanced IWFNDBQuery with columns, where, orderBy, limit properties

2. Added Service Methods (packages/server-ai/src/xpert-table/xpert-table.service.ts)

• queryRows() - Query rows with columns, where, orderBy, limit options
• updateRows() - Update rows with SET values and WHERE conditions
• deleteRows() - Delete rows with WHERE conditions

3. Backend Strategies

• Added WorkflowDBUpdateNodeStrategy - handles database update operations
• Added WorkflowDBDeleteNodeStrategy - handles database delete operations
• Added WorkflowDBQueryNodeStrategy - handles database query operations
• Registered all strategies in plugins index

4. Frontend Components

• Created DB Query panel component (db-query.component.ts, .html, .scss)
• Registered in workflow panel component

Workflow Node Types Available

Node Type	Description
DB_INSERT	Insert rows into a table
DB_UPDATE	Update rows with WHERE conditions
DB_DELETE	Delete rows with WHERE conditions
DB_QUERY	Query rows with columns, where, orderBy, limit
DB_SQL	Execute custom SQL statements

Testing

• All strategies follow the existing pattern used by WorkflowDBInsertNodeStrategy and WorkflowDBSQLNodeStrategy
• Service methods use the existing DBTableDataAction enum from the plugin SDK
• Frontend components follow the existing component structure

Closes #218