feat: Add RyuGraph support with full backwards compatibility for Kuzu

[saksham115]

Description

This PR adds RyuGraph as the new graph store provider while maintaining complete backwards compatibility with existing Kuzu configurations.

Background: Kuzu has been archived and is no longer maintained. RyuGraph is a community-maintained fork of Kuzu with an identical API, ensuring ongoing support and updates.

Key Changes:

• Add ryu_memory.py as native RyuGraph implementation
• Modify kuzu_memory.py to use RyuGraph internally (backwards compatibility wrapper)
• Support both "kuzu" and "ryu" providers in factory and configs
• Add deprecation warnings guiding users to migrate to "ryu" provider
• Update dependency from kuzu>=0.11.0 to ryugraph>=25.9.0

Backwards Compatibility:

• ✅ NO BREAKING CHANGES: Existing code using provider: "kuzu" continues to work without modification
• The "kuzu" provider automatically uses RyuGraph under the hood
• Deprecation warnings guide users to update at their convenience
• No migration required - existing code benefits from RyuGraph automatically

Type of change

• New feature (non-breaking change which adds functionality)
• Documentation update

How Has This Been Tested?

• Unit Test

Test Results:

pytest tests/memory/test_kuzu.py tests/memory/test_ryu.py -v
# ======================== 10 passed, 5 warnings in 0.55s ========================

All tests pass successfully:

• 5 tests for backwards-compatible 'kuzu' provider (shows expected deprecation warnings)
• 5 tests for new 'ryu' provider
• Both providers use RyuGraph internally and work correctly

Test Coverage:

• Initialization with valid and invalid embedding dimensions
• Adding, searching, and deleting graph entities
• Node and edge counting
• Graph operations with filters and metadata

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings (only expected deprecation warnings)
• 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
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Documentation Updates

• Updated docs/changelog.mdx - Added v1.0.1 entry emphasizing backwards compatibility
• Updated docs/open-source/features/graph-memory.mdx - Added both Kuzu (deprecated) and RyuGraph sections
• Updated docs/platform/features/graph-threshold.mdx - Listed both providers
• Restored examples/graph-db-demo/kuzu-example.ipynb with deprecation notice
• Created examples/graph-db-demo/ryu-example.ipynb for new users
• Updated LLM.md and Makefile references
• Created optional migration tool with clear documentation

Files Changed

New Files:

• mem0/memory/ryu_memory.py - Native RyuGraph implementation
• tests/memory/test_ryu.py - Test suite for RyuGraph
• examples/graph-db-demo/ryu-example.ipynb - Example notebook for RyuGraph
• tools/migrate_kuzu_to_ryu.py - Optional migration script

Modified Files:

• mem0/memory/kuzu_memory.py - Wrapper using RyuGraph internally
• mem0/utils/factory.py - Supports both "kuzu" and "ryu" providers
• mem0/graphs/configs.py - Keeps both KuzuConfig and RyuConfig
• tests/memory/test_kuzu.py - Backwards compatibility tests
• examples/graph-db-demo/kuzu-example.ipynb - Added deprecation notice
• pyproject.toml - Updated dependency to ryugraph>=25.9.0
• Makefile - Updated install_all target
• Documentation files (changelog, graph-memory, graph-threshold, LLM.md)

Migration Guide for Users

For existing Kuzu users:

• ✅ Your code continues to work without any changes
• Optional: Update config from provider: "kuzu" to provider: "ryu" at your convenience
• Optional: Run migration script if you want to explicitly understand the migration

For new users:

• Use provider: "ryu" in your configuration
• Install with: pip install "mem0ai[graph]"

Why this change?

• Kuzu has been archived and is no longer maintained
• RyuGraph is a community-maintained fork with ongoing support
• Identical API ensures seamless transition
• Users automatically benefit from maintained software
• Future-proofs the graph store functionality

Maintainer Checklist

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Made sure Checks passed

[CLAassistant]

All committers have signed the CLA.