feature: Global Search and Advanced Filtering for PYQs

[JavaProgswing]

Description

This PR implements a much-needed global search and advanced filtering mechanism on the PYQs page to improve user experience and resource discovery as the repository grows.

Fixes #336

Changes Made:

• Added a searchTerm state and a new search bar input on the PYQs page.
• Updated the dropdown filters (University, Department, Semester, Subject) to default to "All" rather than empty strings, allowing for partial filtering instead of strictly requiring all four filters to be selected simultaneously.
• Modified the filtering logic (filteredPapers) to cross-reference both the search input (matching against subject, uploader, or university) and the dropdown values dynamically in real time.
• Updated the results header to accurately reflect the count of found resources dynamically based on the applied filters.

Type of change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Documentation update

Checklist:

• My code follows the code style and guidelines of this project.
• I have tested the changes locally (search input and dropdown filtering work smoothly).

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