fix: add PDF validation for file picker uploads

[SunnyAgrwl05]

Description

This PR fixes the file validation inconsistency in ResumeDropzone.

Changes Made

• Added PDF validation for files selected through the file picker.
• Ensured non-PDF files trigger the existing hasNonPdfFile error state.
• Kept drag-and-drop and file picker validation behavior consistent.

Testing

• ✅ Selected a PDF file via file picker → imported successfully.
• ✅ Selected a JPEG/non-PDF file via file picker → displayed "Only pdf file is supported".
• ✅ Existing drag-and-drop validation continues to work.

Fixes #67

[SunnyAgrwl05]

Hi @saqibxjaved,

I have fixed this issue and submitted a PR.

PR: #72

The fix adds PDF validation for file picker uploads and ensures non-PDF files trigger the existing error state, keeping drag-and-drop and file picker behavior consistent.

Thank you!