feat: add local storage bookmark functionality

[NiranjanDoijode23]

Related Issue

Fixes #89

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Description

Added a "Save for Later / Bookmark" feature allowing students to easily save topics and access them via a dedicated Bookmarks page. This heavily improves UX by preventing students from having to manually navigate deep into semester folders to find their current reading position.

Changes made:

• Created useBookmarks.ts custom hook utilizing localStorage for state persistence.
• Built a reusable BookmarkButton.tsx component.
• Created a /bookmarks page to display and manage saved topics.
• Added a BOOKMARKS link to both desktop and mobile Navbars.
• Integrated the BookmarkButton into the DSC subject pages (and others).

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Type of Change

• Bug fix
• New feature
• Documentation update
• UI/UX improvement
• Refactor

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Screenshots / Demo

Before - Bookmarks tab And No save option

After - Added Bookmark tab and Save option To continue reading

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How Has This Been Tested?

• Tested locally using npm run dev.
• Verified that localStorage persists data across page reloads and browser restarts.
• Tested responsive design on the Bookmarks page and Mobile Navbar.

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Checklist

• My code follows the project structure and conventions
• I have tested the changes locally
• I have linked the related issue properly
• I have added screenshots where applicable
• No existing functionality was broken

[vercel]

@NiranjanDoijode23 is attempting to deploy a commit to the PushkarScripts Team on Vercel.

A member of the Team first needs to authorize it.

[NiranjanDoijode23]

Hii @pushkarscripts Also Assign me Issue #108 i will resolve the issue related to params in all the sems and subject

[NiranjanDoijode23]

Hii @pushkarscripts Assign me A Runtime Bug #108 and Feature #117 i would like to work on it