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 (`chat/ai/list`).

This change standardizes the encryption process to use the direct `GcmAes256` utility, ensuring compatibility between encryption and decryption, and resolving the data retrieval failures.
To implement this **search_filter** feature, you'll need to modify these architectural layers:


**1. Utils**
   - `crates/router/src/utils/chat.rs`

**Code Patterns Applied:**
- Extend existing types with new fields (2 changes)
{"pr_number": 9562, "pr_title": "fix(chat): alter encryption logic for ai service", "merged_at": "2025-10-01T13:05:25Z", "intent": {"feature_type": "search_filter", "action": "add_feature", "entities": ["merchant"]}, "hierarchy": {"utils": ["crates/router/src/utils/chat.rs"]}, "change_types": {"fields_added": 2, "imports_added": 2}, "has_identifier_data": false, "commits_matched": 0, "match_method": "none"}