refactor(api): move utils/api.py under utils/cache

`utils.api` shadowed `ansible.module_utils.api` for anything that reached the
top-level `utils` package first, which the ai-agent-employees merge made
reachable. The module caches provider declarations, so it belongs beside the
other caches rather than at the root.

The three importers and the two documentation references move with it; nothing
else names the old path.

Verified: `from utils.cache.api import declared_api, provider_enabled,
resolve_api` resolves.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/unit/python/utils/test_api.py

@@ -1,6 +1,6 @@
 import unittest
 
-from utils.api import declared_api, provider_enabled, resolve_api
+from utils.cache.api import declared_api, provider_enabled, resolve_api
 
 
 class TestResolveApi(unittest.TestCase):