Add CLI support for creating and publishing templates

[m-abdelwahab]

Summary

Adds CLI support for creating and publishing Railway templates, matching the dashboard flow while making the workflow usable for agents.

Changes

• Add railway templates create / generate

  • Creates an unpublished template from a project via templateGenerate
  • Defaults to dashboard behavior by generating at the project level
  • Supports explicit --environment when intentionally generating from one environment
  • Supports --json output for agent workflows

• Add railway templates publish <template>

  • Publishes an unpublished template via templatePublish
  • Accepts category, description, README, image, demo project, and workspace
  • Supports README via inline text, file, or stdin
  • Includes dashboard-aligned validation for category, description, README, and image
  • Includes valid categories in help text

• Add GraphQL operations for template generate, publish, and lookup