feat: add prompt caching support for Claude and Nova models

Add comprehensive prompt caching support with flexible control options:

Features:
- ENV variable control (ENABLE_PROMPT_CACHING, default: false)
- Per-request control via extra_body.prompt_caching
- Pattern-based model detection (Claude, Nova)
- Token limit warnings (Nova 20K limit)
- OpenAI-compatible response format (prompt_tokens_details.cached_tokens)

Supported models:
- Claude 3+ models (anthropic.claude-*)
- Nova models (amazon.nova-*)
- Auto-detection prevents breaking unsupported models

Implementation:
- System prompts caching via extra_body.prompt_caching.system
- Messages caching via extra_body.prompt_caching.messages
- Non-streaming and streaming modes
- Compatible with reasoning, thinking, and tool calls

deployment/BedrockProxyFargate.template

@@ -11,6 +11,13 @@ Parameters:
     Type: String
     Default: anthropic.claude-3-sonnet-20240229-v1:0
     Description: The default model ID, please make sure the model ID is supported in the current region
+  EnablePromptCaching:
+    Type: String
+    Default: "false"
+    AllowedValues:
+      - "true"
+      - "false"
+    Description: Enable prompt caching for supported models (Claude, Nova). When enabled, adds cachePoint to system prompts and messages for cost savings.
 Resources:
   VPCB9E5F0B4:
     Type: AWS::EC2::VPC
@@ -251,6 +258,9 @@ Resources:
               Value: "true"
             - Name: ENABLE_APPLICATION_INFERENCE_PROFILES
               Value: "true"
+            - Name: ENABLE_PROMPT_CACHING
+              Value:
+                Ref: EnablePromptCaching
           Essential: true
           Image:
             Ref: ContainerImageUri