feat : add interactive before after comparison slider

[kavin553]

Description

Fixes #706

Added an interactive before/after image comparison slider for AI-processed passport photos.

Features Added

• draggable comparison slider
• responsive mobile interaction
• smooth before/after image preview
• touch-friendly drag support
• lightweight frontend-only implementation
• optimized image comparison UI

Improvements

• enhanced user visual comparison experience
• improved mobile usability
• preserved existing upload and processing workflow
• maintained responsive layout behavior

Type of Change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Manually tested local server
• Frontend build verification

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings

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[kavin553]

Hi @souma9830 👋

I’ve completed the implementation for the Interactive Before/After Image Comparison Slider feature and submitted the changes for review.

Implemented Features

• draggable before/after comparison slider
• smooth image comparison interaction
• responsive mobile-friendly slider behavior
• processed image overlay preview
• optimized lightweight frontend implementation
• preserved existing photo preview functionality
• clean reusable comparison container structure

Validation Completed

• tested slider movement locally
• verified responsive behavior on smaller screens
• confirmed original and processed image rendering
• ensured existing upload/preview workflow remains unaffected
• verified no unrelated files were modified

Looking forward to your feedback and review 🚀