feat(mcp): add temporal graph support to MCP tools

Add Postgres support for temporal facts and enhance MCP tools with type-based routing for unified contextual + temporal memory queries.

BREAKING CHANGE: None (backward compatible via optional parameters)

Changes:
- Add temporal_facts and temporal_edges tables for Postgres
- Add temporal indexes for efficient queries
- Enhance openmemory_store with type parameter (contextual|factual|both)
- Enhance openmemory_query with type parameter (contextual|factual|unified)
- Add fact_pattern parameter for structured temporal queries
- Add comprehensive MCP temporal integration documentation

Author: kishan0725