feat(08-05): decompose documents API monolith into documents/ package — CODE-02 CODE-08
- upload.py: request_upload_url, upload_document, confirm_upload (3 routes)
- crud.py: list_documents, get_document, patch_document, delete_document, classify_document (5 routes)
- content.py: stream_document_content + _parse_range (1 route)
- shared.py: _CLOUD_PROVIDERS, UploadUrlRequest, DocumentPatch (single definitions)
- __init__.py: router aggregator prefix=/api/documents, 9 routes total
- documents.py monolith deleted; all URL paths unchanged
- list_documents registered on parent router to avoid FastAPI empty-path/prefix check
- get_storage_backend_for_document re-exported for test monkeypatching compatibility
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
