publishBulk silently fails on HTTP 500 errors - returns empty failedMessages array

## Bug Description

The `publishBulk` method in the Dapr Node.js SDK has a critical error handling bug where it returns `{ failedMessages: [] }` instead of actual failed entries when the Dapr sidecar returns HTTP 500 errors. This causes applications to incorrectly assume bulk publish operations succeeded when they actually failed.

## Environment

- **Dapr Runtime Version**: v1.15.5
- **Dapr JS SDK Version**: v3.5.2 (latest)
- **Node.js Version**: v18+
- **Platform**: macOS/Linux

## Expected Behavior

When `publishBulk` encounters HTTP 500 errors from the Dapr sidecar, it should return a response with populated `failedMessages` array containing the actual failed entries.

## Actual Behavior

The SDK returns `{ failedMessages: [] }` even when all messages fail to publish, causing applications to incorrectly assume success.

## Root Cause

The bug is in the `handleBulkPublishError` method in `/implementation/Client/HTTPClient/pubsub.js` (lines 65-77). The method fails to properly parse HTTP 500 error responses from the Dapr sidecar.

**Problematic code:**
```javascript
async handleBulkPublishError(entries, error) {
try {
const err = JSON.parse(error.message);
if (err.error_msg) {
const bulkPublishResponse = JSON.parse(err.error_msg);
return (0, Client_util_1.getBulkPublishResponse)({ entries: entries, response: bulkPublishResponse });
}
}
catch (_innerError) {
// Falls through to return empty failedMessages
}
return (0, Client_util_1.getBulkPublishResponse)({ entries: entries, error: error });
}
```

## Reproduction Steps

1. Configure Dapr with a Kafka pubsub component
2. Use `publishBulk` with an invalid/non-existent topic name
3. Observe that Dapr sidecar correctly returns HTTP 500 with error details
4. Check the SDK response - it returns `{ failedMessages: [] }`

## Logs Evidence

**Dapr sidecar correctly detects error:**
```
DEBU[13082] api error: code = Internal desc = error when publishing to topic foo in pubsub pub-sub-kyc3: kafka: Failed to deliver 1 messages.
INFO[13082] HTTP API Called ... code=500 duration=1358 ... size=207
```

**SDK incorrectly returns empty failedMessages:**
```javascript
Dapr publishBulk result: { failedMessages: [] }
```

## Impact

This is a **critical bug** that causes:
- Silent failures in production systems
- Data loss (messages appear published but aren't)
- Incorrect application state (success reported when operations fail)
- Difficult debugging (no indication of failure in application logs)

## Workaround

Currently, applications must implement additional error detection by:
1. Monitoring Dapr sidecar logs directly
2. Implementing custom timeout/retry logic
3. Using alternative publish methods

## Suggested Fix

The `handleBulkPublishError` method needs to properly parse the HTTP 500 error response structure that Dapr returns. The error response contains valid `failedEntries` data that should be extracted and returned to the application.