Avoid logging raw MessageExt bodies in LocalMessageService

## Problem

`LocalMessageService.popMessage` logs a full `MessageExt` when POP offset metadata is inconsistent:

```java
log.warn("Queue offset [{}] of msg is strange, not equal to the stored in msg, {}", msgQueueOffset, messageExt);
```

`MessageExt.toString()` delegates to `Message.toString()`, which prints `Arrays.toString(body)`. This warning can expose message payload bytes in proxy logs.

## Scope

Track 2 / Proxy runtime diagnostics hardening. This should only change log content, not POP offset handling behavior.

## Expected behavior

- Do not log raw `MessageExt` in `LocalMessageService`.
- Keep useful diagnostics such as topic, msgId, queueId, queueOffset, body size, and property keys.
- Add targeted test coverage for the summary helper.

## Evidence

- `proxy/src/main/java/org/apache/rocketmq/proxy/service/message/LocalMessageService.java` logs `messageExt` directly.
- `common/src/main/java/org/apache/rocketmq/common/message/Message.java#toString` includes `Arrays.toString(body)`.

Read proxy/src/main/java/org/apache/rocketmq/proxy/service/message/LocalMessageService.java and inspect the warning in popMessage. Add targeted coverage for the summary helper, ensuring the warning omits raw message body bytes while retaining the requested diagnostics and leaving POP offset handling unchanged.

Written by the indexing model from the issue text.