feat: Jan clarifies model deletion functionality in "My Models"

[eckartal]

Problem
The current model deletion interface under "My Models" is unclear, with some users misunderstanding that the "Delete" action might remove the model files from their storage, whereas it only removes them from the Jan list.

Success Criteria
Update the UI and provide clear messaging that explains the "Delete" action only removes the model from Jan's internal list and does not delete the actual files from the user's device. This can be achieved through tooltip enhancements, confirmation dialogs, or updated UI text.

Additional context
Detailed feedback: https://www.reddit.com/r/LocalLLaMA/comments/1cclmjk/comment/l1byjva/?context=3