Build import/export system for bulk position management

[Smartdevs17]

Description

Create a bulk import/export system allowing users to manage multiple positions via CSV/JSON uploads with transaction batching.

Acceptance Criteria

• CSV/JSON import for batch operations
• Import validation with error reporting
• Export positions in multiple formats
• Template generation for imports
• Import history with rollback capability
• Large file processing with streaming

Technical Scope

• api/src/utils/importExport.ts
• api/src/routes/
• Edge: encoding detection, large file memory management, partial import handling