feat: implement map file import/export functionality

[zuhanit]

Summary

• Add support for importing StarCraft map files (.chk, .scx, .scm) and Webditor project files (.wproject)
• Implement save functionality for Webditor project format
• Add backend endpoint for map file processing

Changes Made

Frontend

• App Menu: Added Open and Save menu items with file input handling
• Map Store: Enhanced with openUsemap action supporting multiple file formats
• Project Store: New store for managing project metadata
• File Handling: Support for both binary map files and JSON project files

Backend

• New Endpoint: /api/v1/maps/open for processing uploaded map files
• Bug Fix: Fixed string section detection in CHK parser
• Test Maps: Added example map files for testing

Features

• Import .chk/.scx/.scm files via backend processing
• Import .wproject files with schema validation (non-destructive)
• Export current map as .wproject JSON format
• Error handling and user feedback for file operations

Technical Details

• Uses Zod safeParse to validate imported data without removing unknown fields
• Maintains compatibility with existing Immer-based state management
• Proper file extension detection and format-specific processing
• TypeScript type safety throughout the import/export pipeline

Test Plan

• Import various StarCraft map formats
• Export and re-import .wproject files
• Verify all entity data preservation during save/load cycles
• Error handling for invalid file formats

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