Add tooltip to Jump to Bottom button

[kevinaboos]

Added a tooltip to the "Jump to Bottom" button.

Why:
The "Jump to Bottom" button is an icon-only button. Adding a tooltip improves accessibility and clarity for users who might not immediately recognize the icon's function.

How:

• Modified src/shared/jump_to_bottom_button.rs to intercept FingerHoverIn and FingerHoverOut events on the inner IconButton.
• Dispatched TooltipAction::HoverIn with the text "Jump to bottom" and position Left (since the button is at the bottom right).
• Dispatched TooltipAction::HoverOut when the hover ends.

Testing:

• Ran cargo check and cargo clippy to ensure no compilation errors or linting issues.
• Verified imports and struct definitions in src/shared/callout_tooltip.rs.

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PR created automatically by Jules for task 13908182130717325989 started by @kevinaboos

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