fix: pass configured Neo4j database to execute_query

[abhinavmathur-atlan]

Summary

Fixes Neo4jDriver.execute_query() so the configured database is passed to the Neo4j driver as the top-level database_ argument instead of being inserted into Cypher parameters_.

This keeps query parameters separate from driver configuration and allows read/search queries to run against the configured database instead of Neo4j's default database.

Type of Change

• Bug fix
• New feature
• Performance improvement
• Documentation/Tests

Objective

Bug fix for configured Neo4j databases: writes already use session(database=self._database), but reads through execute_query() were not selecting the configured database.

Testing

• Unit tests added/updated
• Integration tests added/updated
• All existing tests pass

Validation run:

• uv run --extra dev pytest tests/driver/test_neo4j_driver.py
• uv run --extra dev pytest tests/driver
• uv run --extra dev ruff format graphiti_core/driver/neo4j_driver.py tests/driver/test_neo4j_driver.py
• uv run --extra dev ruff check graphiti_core/driver/neo4j_driver.py tests/driver/test_neo4j_driver.py
• uv run --extra dev pyright ./graphiti_core

I also started DISABLE_FALKORDB=1 DISABLE_KUZU=1 DISABLE_NEPTUNE=1 uv run --extra dev pytest -m "not integration"; it progressed through the driver tests but then hit repeated errors in existing graph tests outside this driver change, so I stopped it and kept the validation scoped to the touched driver path.

Breaking Changes

• This PR contains breaking changes

Checklist

• Code follows project style guidelines (make lint passes)
• Self-review completed
• Documentation updated where necessary
• No secrets or sensitive information committed

Related Issues

Closes #1481