feat: add Claude Sonnet 4.5 support with global cross-region inference (#180)

This commit adds comprehensive support for Claude Sonnet 4.5 (claude-sonnet-4-5-20250929),
Anthropic's most intelligent model with enhanced coding capabilities and complex agent support.

Changes:
- Added global cross-region inference profile discovery (global.anthropic.*)
- Fixed temperature/topP compatibility for Claude Sonnet 4.5 (model doesn't support both simultaneously)
- Fixed reasoning_effort parameter handling to prevent KeyError
- Added extended thinking/interleaved thinking support via extra_body parameter
- Updated documentation with Claude Sonnet 4.5 examples (English and Chinese)
- Updated README with Sonnet 4.5 announcement

Technical Details:
- src/api/models/bedrock.py: Added global profile support in list_bedrock_models()
- src/api/models/bedrock.py: Added Claude Sonnet 4.5 detection to remove topP parameter
- src/api/models/bedrock.py: Changed pop("topP") to pop("topP", None) to prevent KeyError
- docs/Usage.md: Added Chat Completions section with Sonnet 4.5 examples
- docs/Usage.md: Updated Interleaved thinking section with Sonnet 4.5 examples
- docs/Usage_CN.md: Added Chinese versions of all Sonnet 4.5 documentation

Model ID: global.anthropic.claude-sonnet-4-5-20250929-v1:0

src/api/models/bedrock.py

@@ -158,6 +158,11 @@ def list_bedrock_models() -> dict:
             if profile_id in profile_list:
                 model_list[profile_id] = {"modalities": input_modalities}
 
+            # Add global cross-region inference profiles
+            global_profile_id = "global." + model_id
+            if global_profile_id in profile_list:
+                model_list[global_profile_id] = {"modalities": input_modalities}
+
             # Add application inference profiles (emit all profiles for this model)
             if model_id in app_profiles_by_model:
                 for profile_arn in app_profiles_by_model[model_id]:
@@ -521,6 +526,11 @@ class BedrockModel(BaseChatModel):
             "topP": chat_request.top_p,
         }
 
+        # Claude Sonnet 4.5 doesn't support both temperature and topP
+        # Remove topP for this model
+        if "claude-sonnet-4-5" in chat_request.model.lower():
+            inference_config.pop("topP", None)
+
         if chat_request.stop is not None:
             stop = chat_request.stop
             if isinstance(stop, str):
@@ -547,7 +557,7 @@ class BedrockModel(BaseChatModel):
             )
             inference_config["maxTokens"] = max_tokens
             # unset topP - Not supported
-            inference_config.pop("topP")
+            inference_config.pop("topP", None)
 
             args["additionalModelRequestFields"] = {
                 "reasoning_config": {"type": "enabled", "budget_tokens": budget_tokens}
@@ -573,8 +583,12 @@ class BedrockModel(BaseChatModel):
             args["toolConfig"] = tool_config
         # add Additional fields to enable extend thinking
         if chat_request.extra_body:
-            # reasoning_config will not be used 
+            # reasoning_config will not be used
             args["additionalModelRequestFields"] = chat_request.extra_body
+            # Extended thinking doesn't support both temperature and topP
+            # Remove topP to avoid validation error
+            if "thinking" in chat_request.extra_body:
+                inference_config.pop("topP", None)
         return args
 
     def _create_response(