fix: disable prompt caching for claude-sonnet-4.5

Explicitly set drop_params and supports_prompt_caching=false for
claude-sonnet-4.5 model to prevent prompt_cache_key parameter from
being sent to Anthropic API.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

ai/litellm-config.yaml

@@ -8,6 +8,8 @@ model_list:
     litellm_params:
       model: anthropic/claude-sonnet-4-5-20250929
       api_key: os.environ/ANTHROPIC_API_KEY
+      drop_params: true
+      supports_prompt_caching: false
 
   - model_name: claude-3-5-sonnet
     litellm_params: