♻️(api) remove bulk operations, rename documents to resources

[StephanMeijer]

Important

Please merge first: #131, #138

Summary

• Rename URL paths from /documents/ to /resources/
• Remove bulk indexing: POST /resources/index/ accepts single doc only (returns 400 for arrays)
• Replace bulk delete with RESTful DELETE /resources/<uuid>/ (204/404/403)
• Refactor demo and test utilities to use single-doc API calls

Breaking Changes

BREAKING CHANGE: API endpoints renamed and bulk operations removed.

Before	After
POST /api/v1.0/documents/index/ (bulk)	POST /api/v1.0/resources/index/ (single)
POST /api/v1.0/documents/delete/ (bulk)	DELETE /api/v1.0/resources/<uuid>/
POST /api/v1.0/documents/search/	POST /api/v1.0/resources/search/

Changes

• core/urls.py: Renamed paths, added UUID path param for delete
• core/views.py: IndexDocumentView rejects arrays, new DeleteDocumentView
• core/schemas.py: Removed DeleteDocumentsSchema
• demo/create_demo.py: Loop with single-doc API calls
• core/utils.py: prepare_index() accepts service param, uses APIClient
• Tests: Deleted old bulk tests, added 30 new single-doc tests
• Docs: Updated endpoint paths in setup guides

Testing

All 30 new tests pass:

• test_api_resources_index.py: 26 tests (single doc, validation, auth)
• test_api_resources_delete.py: 4 tests (success, 404, 403, invalid UUID)

[StephanMeijer]

Important

This PR will be superseded by the next.