feat(api): filter listed memories by scope

[wayyoungboy]

Summary

Closes #1014.

• Add scope query parameter to GET /api/v1/memories for metadata scope filtering.
• Pass metadata filters through API, service, core memory, and storage count/list paths.
• Keep pagination stable by applying metadata filters before limit/offset.
• Document the new REST query parameter and add regression tests for personal/group-style scope pagination.

Validation

• pytest tests/unit/test_list_memory_filters.py tests/unit/test_memory.py -q
• PYTHONPATH=src pytest tests/unit -q
• python3 -m flake8 src/server/api/v1/memories.py src/server/services/memory_service.py src/powermem/core/memory.py src/powermem/storage/adapter.py tests/unit/test_list_memory_filters.py --select=F601,F821,E999
• git diff --check

[lightzt99]

A small suggestion:

it might be worth pushing the scope filter down to the DB layer rather than relying on in-memory filtering. The SQLite backend already supports json_extract-based filtering on nested payload paths via _json_path_for_key (sqlite_vector_store.py:20) — it just needs the adapter to translate the logical key to the backend-specific path:

• SQLite: scope → metadata.scope → json_extract(payload, '$.metadata.scope') = 'personal'
• OceanBase: scope → filter on the metadata JSON column directly

Both list() and count() on the vector stores already accept arbitrary filter keys with dotted nesting. If the adapter does this translation, the has_extra_filters / fetch-all / in-memory paginate branch could be dropped, keeping pagination and counting at the DB level and avoiding the large-fetch risk on bigger datasets.

[wayyoungboy]

Thanks for the suggestion. I pushed an update that translates logical metadata filters before calling the vector store, so list/count no longer fetch all rows for scope filtering. SQLite and PGVector now use nested payload paths such as metadata.scope, while OceanBase keeps scope so its metadata JSON column filter is used directly.\n\nValidation done:\n- targeted scope/list tests passed\n- full unit suite passed: 421 passed\n- started the API server locally and verified the real GET /api/v1/memories flow: created 4 memories with personal/group scopes, confirmed scope=personal returned total 3 with correct paginated results, confirmed scope=group returned total 1, then cleaned up the 4 test memories

[lightzt99]

LGTM