chore: remove generated Dagger SDK files

Remove auto-generated dagger.gen.go files from version control:
- dagger/dagger.gen.go (380 lines): main dispatch logic, invoke handlers, error conversion
- dagger/internal/dagger/dagger.gen.go (14,582 lines): complete Dagger Go SDK client bindings

These files are regenerated by Dagger tooling and should not be committed.

Author: Mohamed Chorfa