feat(mcp): increase default HTTP proxy timeout from 60s to 5 minutes

MCP tool calls often back long-running operations like database queries
or Lambda invocations that routinely exceed 60 seconds. The previous
default caused consistent timeouts for legitimate use cases.

The .timeout(Duration) builder method remains available for callers who
need a specific value. This change only affects the fallback default
when no timeout is explicitly configured.

Author: Alexandre Zajac

mcp/mcp-server/src/main/java/software/amazon/smithy/java/mcp/server/HttpMcpProxy.java

@@ -47,7 +47,7 @@ private HttpMcpProxy(Builder builder) {
         this.endpoint = URI.create(builder.endpoint);
         this.name = builder.name != null ? builder.name : sanitizeName(endpoint.getHost());
         this.signer = builder.signer;
-        this.timeout = builder.timeout != null ? builder.timeout : Duration.ofSeconds(60);
+        this.timeout = builder.timeout != null ? builder.timeout : Duration.ofMinutes(5);
     }
 
     private static String sanitizeName(String host) {