fix: Sanitize entity type labels in graph memory Cypher queries

[mpotter]

Description

This PR fixes an issue where entity types with special characters (e.g., "Person-Name", "City/State", "Entity@Type#123") would cause Cypher query syntax errors when used as node labels in Neo4j graph database queries.

Changes:

• Add sanitizeLabel function to replace special characters with underscores
• Ensures valid Cypher syntax for node labels in Neo4j queries
• Labels are now sanitized to use only alphanumeric characters and underscores, matching the pattern used in the Python implementation

Implementation:

• Modified _addEntities method in graph_memory.ts to sanitize sourceType and destinationType before using them in Cypher queries
• The sanitization function uses regex pattern /[^A-Za-z0-9_]/g to replace invalid characters with underscores
• Function is defined at method scope (outside the loop) for efficiency and consistency with existing code patterns

Fixes a similar issue #3020 that was fixed in the python implementation

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Unit Test

Added comprehensive unit tests in graph_memory.test.ts covering:

• Special characters: Entity types like "Person-Name" and "City/State" are sanitized to "Person_Name" and "City_State"
• Multiple special characters: Labels like "Entity@Type#123" are sanitized to "Entity_Type_123"
• Edge cases: Labels with only special characters (e.g., "---" → "___") and unknown entity types
• Normal labels: Labels without special characters (e.g., "Person", "City") remain unchanged

Test Configuration:

• Tests use mocked Neo4j driver and session to verify Cypher queries contain sanitized labels
• All 5 test cases pass successfully
• Tests verify that sanitized labels appear in the generated Cypher queries and original unsanitized labels do not

To reproduce:

cd mem0-ts
npm run test:ts -- graph_memory.test.ts

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
• 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

Maintainer Checklist

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

[CLAassistant]

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