docs: add comprehensive MCP host configuration documentation

Add complete documentation suite for MCP host configuration management
system following organizational documentation standards.

Documentation includes:
- Implementation Guide: Complete architecture overview, usage examples,
  testing information, and integration patterns
- API Reference: Comprehensive API documentation with examples for all
  models, managers, strategies, and decorators
- Performance considerations and error handling patterns
- Migration guidance and future enhancement roadmap

Key documentation features:
- Decorator-based strategy registration patterns
- Consolidated MCPServerConfig model usage examples
- Inheritance architecture explanation (Claude/Cursor families)
- Environment data structure with corrected v2 constraints
- Integration with backup system for atomic operations
- Comprehensive test coverage documentation (74 tests, 100% pass rate)

Documentation demonstrates successful implementation of v2 architecture
with decorator-based automatic discovery, consolidated Pydantic models,
and inheritance patterns for code reuse and maintainability.

Author: LittleCoinCoin