feat: Add a translation history panel to the popup #44

Is your feature request related to a problem?

If a user translates a code snippet, the result is ephemeral. Once they navigate away from the page or close the tab, the translation is lost. There is no way to retrieve past translations without finding the original code and running the translation again.

Describe the solution you'd like

1. Add a new "History" tab to the main popup.html interface.

2. When a successful translation is completed, store a record of the translation in chrome.storage.local. This record should contain the original code, the translated code, the target language, and a timestamp.

3. The new "History" panel should display a list of the 20 most recent translations. Each item in the list should be clickable, allowing a user to easily view and copy the code.

4. A "Clear History" button should be included to allow users to wipe all saved records.

Additional context

This feature significantly improves the extension's utility, acting as a persistent log of a user's activity. It turns a one-off tool into a personal knowledge base, greatly increasing user retention.