Apply Config CLI Commands to All Components

## Overview

Apply the implemented config CLI commands (show, diff, validate, schema, set/get, migrate) to all Backend.AI components.

## Components

- Manager (reference implementation)
- Agent
- Storage Proxy
- Webserver
- App Proxy Coordinator
- App Proxy Worker

## Requirements

- Each component's CLI module includes config subcommands
- CLI commands use component-specific config schema
- Consistent UX across all components

## Dependencies

Depends on base CLI implementations:

- BA-3473: config show
- BA-3474: config diff
- BA-3475: config validate
- BA-3476: config schema
- BA-3477: config set/get
- BA-3478: config migrate

## Acceptance Criteria

- [ ] Agent CLI has config commands
- [ ] Storage Proxy CLI has config commands
- [ ] Webserver CLI has config commands
- [ ] App Proxy Coordinator CLI has config commands
- [ ] App Proxy Worker CLI has config commands
- [ ] All commands work consistently across components

JIRA Issue: BA-3479