Implement config schema CLI Command

## Overview

Implement `config schema` CLI command that displays the configuration schema with field descriptions, types, and default values.

## Requirements

- Display complete config schema structure
- Show field types, descriptions, and default values
- Show required vs optional fields
- Support filtering by section
- Output in human-readable and JSON Schema format

## Use Cases

1. Discover available config options
1. Check field types and constraints
1. Generate documentation
1. Integration with external tools (JSON Schema export)

## Acceptance Criteria

- [ ] Shows all config fields with types and descriptions
- [ ] Indicates required vs optional fields
- [ ] Shows default values where applicable
- [ ] Supports --format option (table, json-schema)
- [ ] Supports --section option for filtering
- [ ] Works for all components

JIRA Issue: BA-3476