perf: Optimize chat message loading performance and message ordering

[hundredwz]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

During performance optimization work, I identified two areas for improvement in our chat message handling:

1. The current implementation makes multiple SQL queries when fetching dialogue content, which is not optimal for performance, especially when dealing with large conversation histories.
2. The message ordering in service_api is inconsistent with our documentation. While this doesn't affect functionality, maintaining consistency across our codebase and documentation is important for maintainability and developer experience.

2. Additional context or comments

Current situation:

1. Multiple SQL queries are executed to fetch chat messages
2. Message ordering in service_api differs from documentation specification

Proposed improvements:

1. Optimize the dialogue content fetching logic to reduce the number of database queries
2. Align service_api message ordering with documentation (implementing descending order)

Expected benefits:

1. Improved performance through reduced database load
2. Better code consistency and maintainability
3. Enhanced alignment between implementation and documentation

Note: This is a proactive optimization effort. While the current implementation is functional, these improvements will help enhance system performance and maintain code quality standards.

3. Can you help us with this feature?

• I am interested in contributing to this feature.