Implement ecdn rate-limit commands (list/create/get/update/delete)

Summary

The eCDN rate-limit commands were documented but never implemented. These commands would manage rate limiting rules on CDN zones.

Commands to Implement

• b2c ecdn rate-limit list — List rate limiting rules
• b2c ecdn rate-limit create — Create a rate limiting rule
• b2c ecdn rate-limit get — Get a rate limiting rule
• b2c ecdn rate-limit update — Update a rate limiting rule
• b2c ecdn rate-limit delete — Delete a rate limiting rule

Context

Discovered during v1.0 GA readiness audit. Documentation and oclif topic entries were removed in the cleanup PR.

Start by locating the existing b2c ecdn CLI entry points and neighboring commands, then review the documented rate-limit behavior and the cleanup that removed the documentation and oclif topic entries. Done means implementing list, create, get, update, and delete for CDN-zone rate-limiting rules, with the command behavior and inputs aligned to the available API.