Add high-priority test suites covering:

HTTP Server Tests (16 tests):
- Server configuration (CORS, JSON middleware)
- Health endpoint (status, version, response time, concurrency)
- Message endpoint (405 error handling)
- Error handling (invalid routes, malformed requests)

CLI Tests (23 tests):
- Mode selection (stdio vs HTTP)
- Port configuration (default, custom, short/long flags)
- Version and help information
- Argument combinations and edge cases

Tool Registration Tests (128 tests):
- All 16 tools verified for exports (name, description, schema, execute)
- Tool naming conventions (snake_case, ynab_ prefix)
- Input schema validation
- Execute function signatures
- Registration process verification

SSE Connection Tests (21 tests):
- Connection handling and lifecycle
- Multiple concurrent connections
- Transport configuration
- Server configuration per connection
- CORS and request headers
- Error handling

All 357 tests passing (169 existing + 188 new)
Test coverage for HTTP server, CLI parsing, tool registration, and SSE transport

Docker Changes:
- Update Dockerfile to run in HTTP mode with --http flag
- Expose port 3000 for HTTP server access
- Set default port to 3000 (configurable via CMD override)
- Add .dockerignore for optimized Docker builds (excludes node_modules, tests, etc)

Documentation Updates:
- Add comprehensive Docker deployment section to README
- Include examples for building, running, health checks, and logs
- Document custom port configuration for Docker
- Add Docker quick reference to CLAUDE.md

This enables easy containerized deployment of the YNAB MCP server
with HTTP/SSE transport for remote access scenarios.

Dockerfile Changes:
- Add --platform=linux/amd64 to FROM instruction for consistent builds
- Change default port from 3000 to 80 (standard HTTP port)
- Update EXPOSE directive to port 80
- Update CMD to use --port 80

Documentation Updates:
- Update README.md Docker section with port 80 examples
- Add port mapping examples (80:80, 3000:80, custom ports)
- Document multi-platform build options using buildx
- Update CLAUDE.md Docker quick reference to use port 80
- Add example for mapping container port 80 to host port 3000

This provides a standard HTTP port configuration for Docker deployments
while maintaining flexibility for custom port mappings.