[BUG]: Decryption failure in chat prevents retrieval of conversation history

Internal users are unable to view their past chat conversations through the chat/ai/list endpoint, which is meant to be used for internal users. When attempting to retrieve the chat history, the system fails to decrypt the stored messages, resulting in error.
<think>
PR Context:
- Title: fix(chat): alter encryption logic for ai service
- Merged: 2025-10-01T13:05:25Z
- Files changed: 1 files
- Commits: 2 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [x] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
This PR addresses an issue where chat conversation history could not be decrypted in the `chat/ai/list` endpoint. The root cause was an inconsistency between the encryption method used when storing chat interactions (`chat/ai/data`) and the decryption method used when retrieving them 
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** fix(chat): alter encryption logic for ai service (#9562)
Files to modify:


**crates/router/src/utils/chat.rs**
  Modify existing code
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