feat: Add FalkorDB Target

[galshubeli]

Description

This PR adds FalkorDB as a new built-in property graph target for CocoIndex. FalkorDB is a high-performance graph database built on Redis that provides ultra-fast graph operations and Cypher query support.

Changes Made

• New FalkorDB Target Implementation (rust/cocoindex/src/ops/targets/falkordb.rs)

  • Full support for nodes and relationships
  • Vector index support for semantic search
  • Full-text search (FTS) index support
  • Batch operations for efficient data loading
  • Connection management with Redis-based backend

• Python Bindings (python/cocoindex/targets/_engine_builtin_specs.py)

  • FalkorDBConnection - connection specification
  • FalkorDB - target specification
  • FalkorDBDeclaration - declaration specification for nodes

• Complete Working Example (examples/docs_to_knowledge_graph_falkordb/)

  • Document-to-knowledge-graph pipeline using LLM extraction
  • Comprehensive README with setup instructions
  • Shows nodes, relationships, and entity mentions

• Dependencies

  • Added falkordb crate (v0.1.11) to Cargo.toml

Motivation and Context

FalkorDB offers several advantages:

• Performance: Built on Redis for ultra-fast graph operations
• Ease of deployment: Simple Docker-based setup, no complex installation
• Compatibility: Uses standard Cypher query language
• Lightweight: Minimal resource footprint compared to traditional graph databases

This addition provides users with an alternative to Neo4j that's easier to deploy for local development and smaller-scale production workloads.

Breaking Changes

❌ No breaking changes - This is a purely additive feature.

Testing

• ✅ Pre-commit hooks pass (formatting, linting)
• ✅ Example tested locally with FalkorDB running in Docker
• ✅ Successfully creates nodes, relationships, and indexes
• ✅ Vector and FTS indexes working correctly

Related Issues

Closes # (if there's a related issue, add the number here)

Checklist

• Code follows the existing patterns (mirrors Neo4j implementation)
• Added comprehensive example with documentation
• Pre-commit checks pass
• Dependencies properly declared
• Example README includes setup and usage instructions

[badmonster0]

@galshubeli thanks a lot for the PR, we'll get on it shortly!

[georgeh0]

@galshubeli thanks a lot for the PR! The code change looks good! Can you merge with the latest main branch and push again?