Group notebook summaries and transcripts under parent SummaryGroup (#233)

[allenporter]

Description

Fixes #233.

In the Supernote ecosystem and Partner App, digests belonging to the same notebook/document are grouped under a parent SummaryGroup (is_summary_group="Y" / True). Previously, SummaryModule produced root-level summaries (parent_unique_identifier=None) for raw OCR transcripts and Gemini summaries, leading to an unorganized flat digest list in the app.

Changes

1. Identifier Utilities:
   • Added get_summary_group_id(file_basis: str) -> str in supernote.server.utils.paths returning {file_basis}-group.
2. Processor Module:
   • Implemented _upsert_group in SummaryModule to ensure a SummaryGroup exists for each note before adding/updating summaries.
   • Linked both the OCR transcript ({file_basis}-transcript) and AI summary ({file_basis}-summary) to the parent group by setting parent_unique_identifier.
3. Summary Service:
   • Updated SummaryService.update_summary to support updating parent_unique_identifier, source_path, and data_source when provided in UpdateSummaryDTO.
4. Testing:
   • Added tests/server/utils/test_paths.py for full 1:1 test parity.
   • Updated unit tests in test_summary.py to verify group creation/updates and parent_unique_identifier propagation.
   • Updated integration test in test_processor_integration.py to assert database group creation and child summary hierarchy.

Verification

• Full test suite passed (597 tests).
• Ruff check & format verified clean.