feat: Optional pagination list methods

[drish]

• Domains
• Audiences
• Api Keys
• Contacts
• Broadcasts

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Summary by cubic

Adds optional pagination to list methods for API Keys, Audiences, Broadcasts, Contacts, and Domains, enabling limit/after/before queries and returning pagination metadata. Updated examples and tests to demonstrate and verify the new behavior.

• New Features
  • List methods accept optional params: limit, after, before.
  • List responses include object: "list" and has_more.
  • Added PaginationHelper to build query strings safely (filters None, preserves existing queries).
  • Updated examples to show paginated usage for each resource.
  • Added comprehensive tests for list pagination and the helper.

[lucasfcosta]

LGTM! Just one minor suggestion about the docstrings on whether we want to make it more explicit that not passing limit will not paginate. Just in case people think we'll paginate to the max (100 results) by default (which we don't do).