fix(frontend): restore sidebar resize button and functionality (#9370)

[CodeOtaku-01]

Description

This PR fixes issue #9370 where the sidebar resize (expand/collapse) button was missing from the UI and non-functional when the sidebar was closed.

Changes Made

• SideNav Component: Restored the collapse-expand-handlers div and added handleTogglePinned prop.
• AppLayout Integration: Passed the handleToggleSidebar function to SideNav so the button can trigger the state change.
• Styling: Updated SideNav.styles.scss to make the button visible and added premium hover/interactive styles.
• Icons: Used ChevronLeft and ChevronRight from lucide-react to clearly indicate the button's action.

Verification Results

• Verified that the button is now visible at the bottom of the sidebar.
• Confirmed that clicking the button successfully toggles the sidebar state between collapsed and expanded.
• Fixed a syntax error in the component props that was causing TypeScript lint errors.

Fixes #9370

---

Note

Low Risk
Low risk UI change: adds a missing sidebar toggle control and styles; main risk is minor layout/CSS regressions or incorrect toggle state wiring.

Overview
Restores the sidebar collapse/expand button in SideNav and wires it to the existing toggle logic via a new handleTogglePinned prop passed from AppLayout.

Updates the collapse-expand-handlers styles to ensure the control is visible and adds hover/interaction styling, and uses ChevronLeft/ChevronRight icons to reflect the pinned state.

^{Reviewed by Cursor Bugbot for commit 2594363. Bugbot is set up for automated code reviews on this repo. Configure here.}

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 2594363. Configure here.}

[H4ad]

Thanks for the PR, can you please add a video about the fix before and after the change?