fix(proxy): replace unwrap/expect with graceful error handling

- Handle HTTP client initialization failure with no_proxy fallback
- Fix potential panic on Unicode slicing in API key preview
- Add proper error handling for response body builder
- Handle edge case where SystemTime is before UNIX_EPOCH

src-tauri/src/proxy/handlers.rs

@@ -291,7 +291,10 @@ async fn handle_claude_transform(
     );
 
     let body = axum::body::Body::from(response_body);
-    Ok(builder.body(body).unwrap())
+    builder.body(body).map_err(|e| {
+        log::error!("[Claude] 构建响应失败: {e}");
+        ProxyError::Internal(format!("Failed to build response: {e}"))
+    })
 }
 
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