fix(memory): deduplicate episodic/event_log on re-memorize and add foresight expiry cleanup

[dugubuyan]

Description

The memory write pipeline was append-only across all three stores (MongoDB, Elasticsearch, Milvus). This PR fixes two data quality issues that result from that behaviour.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test improvements
• Build/CI/CD changes

Related Issues

Fixes #95
Relates to #

Changes Made

• Add delete-before-insert deduplication for episodic_memory and event_log: when the same MemCell is re-processed, old records are removed from all three stores before the new ones are written. Deduplication key is (parent_id, user_id) to correctly handle group vs personal episodes from the same source.
• Add cleanup_expired_foresights() in src/biz_layer/mem_cleanup.py: deletes foresight records whose end_time has passed from Milvus → Elasticsearch → MongoDB in that order.
• Add delete_by_parent_id to EpisodicMemoryRawRepository, EpisodicMemoryEsRepository, and EpisodicMemoryMilvusRepository.
• Add delete_by_parent_id to EventLogEsRepository.
• Add delete_expired to ForesightRecordRawRepository and ForesightEsRepository.

Testing

• Tested locally with manual verification
• Added/updated unit tests
• Added/updated integration tests
• All existing tests pass

Test Configuration:

• OS: macOS
• Python version: 3.12
• Database versions (if relevant):

Test Results:

PYTHONPATH=src uv run pytest tests/
--ignore=tests/test_embedding_reranker_providers.py
--ignore=tests/test_keyword_vocabulary_milvus_repository.py
--ignore=tests/test_stability_integration.py -q

136 failed, 105 passed
The 136 failures are pre-existing in the upstream repo (integration tests requiring live database connections). Result is identical before and after this change.

Checklist

• My code follows the project's code style guidelines
• I have performed a self-review of my code
• I have commented my code where necessary, particularly in complex areas
• I have updated the documentation accordingly
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have used Gitmoji in my commit messages
• Any dependent changes have been merged and published

Screenshots (if applicable)

Additional Notes

cleanup_expired_foresights() is provided as a standalone async function intended to be wired into a scheduled task (e.g. via the existing core/asynctasks/ framework or ARQ). The deletion order (Milvus → ES → MongoDB) ensures that even if a later step fails, the record is no longer returned by search.

Breaking Changes

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.