Add limit parameter to search()/search_v2()

[Vitexus]

Summary

• /api/v1/search and /api/v2/search accept a limit query parameter, but search()/search_v1()/search_v2() didn't expose it, so passing limit= raised TypeError: got an unexpected keyword argument 'limit'.
• Adds limit: Optional[int] = None to search() and search_v2() and forwards it through to the API request params via the existing __generate_params(locals()) mechanism (it's dropped automatically when None).
• search_v1() is left unchanged (pre-2.4.1, and search() already doesn't forward newer-only params to it).

Fixes #444

Test plan

• Verified via inspect.signature that limit is now accepted by search() / search_v2().
• No new VCR cassette was recorded (would require a live test instance); a maintainer with the test fixture instance may want to add one exercising limit=.