Add new POST endpoint /api/v1/skills/upload for uploading skill zip files.
The endpoint:
- Accepts zip files with bot_id parameter
- Validates file format (must be .zip)
- Saves zip to projects/uploads/{bot_id}/skill_zip/
- Automatically extracts to projects/uploads/{bot_id}/skills/{skill_name}/
- Returns success response with file and extract paths
This enables programmatic skill deployment for specific bots.
