fix: Make CI workflow reusable for PyPI publishing

The PyPI publish workflow was failing because it calls the CI workflow
with 'uses:', but CI workflow was missing the required 'workflow_call'
trigger that makes it reusable.

Changes:
- Add workflow_call trigger to CI workflow
- Allows PyPI workflow to successfully call CI as a reusable workflow

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: codebydivine

.github/workflows/ci.yml

@@ -6,6 +6,7 @@ on:
     tags: [ 'v*' ]
   pull_request:
     branches: [ main, develop ]
+  workflow_call:
 
 jobs:
   test: