Add Support for Uploading PPT Files to Generate Quizzes

Currently, the platform allows quiz generation from text input and document URLs, but it does not support uploading PowerPoint (.ppt / .pptx) files. Many users rely on PPTs for lectures, presentations, and study material, so adding PPT support would significantly improve usability and adoption.

By enabling PPT uploads, users can directly generate quizzes from their presentation slides without needing to copy content manually or convert files beforehand.

### Use Cases:

Teachers uploading lecture slides to generate quizzes for students
Students uploading class PPTs for self-assessment
Trainers generating quick evaluations from presentation decks

### Expected Behavior:

Allow users to upload .ppt / .pptx files
Extract text/content from slides
Use the extracted content to generate quizzes
Show clear validation/errors for unsupported or empty files

### Current Behavior:

PPT files are not accepted as an input source
Users must manually copy content or convert the file elsewhere

### Proposed Enhancement:

Add PPT as a supported input type in both Web and Extension
Parse slides using a PPT parser (python-pptx)
Feed extracted text into the existing quiz-generation pipeline
Add file validation and user-friendly error messages

### Impact:

Improves user experience and workflow
Reduces friction for educators and students
Makes the product more versatile and classroom-friendly