[Feature]: Add Optional Timestamps for Q&A Context (Similar to RikkaHub/Shizuku-style metadata)

### Issue Checklist

- [x] I understand that issues are for reporting problems and requesting features, not for off-topic comments, and I will provide as much detail as possible to help resolve the issue.
- [x] I have checked the pinned issues and searched through the existing [open issues](https://github.com/CherryHQ/cherry-studio/issues), [closed issues](https://github.com/CherryHQ/cherry-studio/issues?q=is%3Aissue%20state%3Aclosed), and [discussions](https://github.com/CherryHQ/cherry-studio/discussions) and did not find a similar suggestion.
- [x] I have provided a short and descriptive title so that developers can quickly understand the issue when browsing the issue list, rather than vague titles like "A suggestion" or "Stuck."
- [x] The latest version of Cherry Studio does not include the feature I am suggesting.

### Platform

Windows

### Version

1.9.11

### Is your feature request related to an existing issue?

Description:
I suggest adding a feature to include timestamps in each Q&A interaction. This is inspired by the Android framework "RikkaHub" (and similar tools), where precise temporal data helps the system understand the flow of time and resolve database/knowledge cutoff conflicts.

The Problem:
Currently, AI models often suffer from "temporal misalignment" due to their training data cutoffs. Many models still perceive the current date as 2024 or 2025. Without a consistent real-time reference point, the AI cannot accurately process time-sensitive information.

Key Benefits:

Resolving Temporal Conflicts: By injecting a system-level timestamp into the context, the AI can immediately recognize the current date/time, overriding outdated internal knowledge.
Enhanced Contextual Awareness: This allows the AI to track durations and intervals.
Example: For healthcare or habit tracking, the AI could say: "Today is the 10th day of your medication cycle. How are you feeling today?" instead of just treating each prompt as a static event.
Improved Longitudinal Tracking: It helps the AI understand the "time span" between different user queries in the same session.

### Desired Solution

Implement a toggle/option to automatically inject the current date and time (timestamp) into the metadata of each message in the conversation history.

### Alternative Solutions

_No response_

### Additional Information

_No response_

No files, tests, or entry points are named in the issue. Start by locating where conversation history is assembled and where feature settings are defined, then determine how optional timestamps should be represented in message metadata. Done means an opt-in toggle injects the current date and time into each Q&A message context, with coverage for enabled and disabled behavior.

Written by the indexing model from the issue text.