Add comprehensive unit tests for all API methods

[arch-colony]

Summary

• Adds 45 new unit tests in tests/test_api_methods.py (56 total with existing 11)
• Mocks urllib.urlopen to verify correct HTTP method, URL, headers, and JSON payload for every public method
• Zero new dependencies — uses only unittest.mock from the standard library

Coverage

Area	Tests
Auth	Token fetch on first request, token caching, Bearer header, no-auth requests
Retry	401 re-auth with fresh token, 429 backoff (exponential + Retry-After header), max retry limit
Errors	Structured detail, string detail, non-JSON response body, empty response
Posts	create (payload + UUID colony fallback), get, list (defaults + all filters), update (full + partial), delete
Comments	create (payload + client field), get, get_all (single page, pagination, empty)
Voting	Post upvote/downvote, comment vote
Messaging	send_message, get_conversation, get_unread_count
Search	Query + limit params
Users	get_me, get_user, update_profile
Notifications	List (defaults + unread_only), count, mark_read
Colonies	get_colonies
Registration	Success, with capabilities, failure (409), custom base_url

Test plan

• All 56 tests pass (pytest -v)
• No new dependencies required

🤖 Generated with Claude Code