@W-20893605 Add eCDN CLI commands and SDK client

[clavery]

Summary

Implements comprehensive CLI support for managing eCDN (embedded Content Delivery Network) zones through the CDN Zones API.

SDK Client

• New createCdnZonesClient function with OpenAPI-typed client
• OAuth scopes: sfcc.cdn-zones (read) and sfcc.cdn-zones.rw (write)
• Helper toOrganizationId() for tenant ID to org ID conversion

CLI Commands (~60 commands)

Topic	Commands
ecdn zones	list, create
ecdn cache	purge, ocapi-toggle
ecdn certificates	list, add, get, update, delete, validate
ecdn security	get, update
ecdn speed	get, update
ecdn cipher-suites	get, update
ecdn origin-headers	get, set, delete
ecdn mtls	list, create, get, delete
ecdn logpush	ownership, jobs (list, create, get, update, delete)
ecdn page-shield	notifications (list, create, delete), policies (list, create, get, update, delete), scripts (list, get)
ecdn mrt-rules	get, create, update, delete, rules (update, delete)
ecdn waf	groups (list, update), rules (list, get, update), rulesets (list, update), managed-rules (list, update), owasp (get, update), migrate
ecdn firewall	list, create, get, update, delete, reorder
ecdn rate-limit	list, create, get, update, delete

Features

• Zone resolution by name or ID (case-insensitive lookup)
• Table output with configurable columns
• JSON output mode for scripting
• Comprehensive flag support for all API options

Testing

• SDK client tests with MSW mocking
• CLI command tests for representative commands (zones/list, cache/purge, security/get, security/update)
• Test helpers for eCDN command stubbing

Documentation

• CLI reference documentation (docs/cli/ecdn.md)
• User skill documentation (plugins/b2c-cli/skills/b2c-ecdn/SKILL.md)