fix: enhance image processing and file validation in scrub_exif function

[monu808]

Fixes #1561

Problem

The scrub_exif() function had security vulnerabilities:

• Generic except Exception silently returned unprocessed files with EXIF intact
• No file size validation (DoS risk)
• No format allowlist (malicious file uploads)
• No decompression bomb protection (memory exhaustion)
• Silent failures allowed bypassing security checks

Solution

Complete refactor with security-first approach:

1. Pre-processing validation: File size check before loading into memory
2. Format allowlist: Only JPEG, PNG, WEBP allowed
3. Decompression bomb protection: Catches DecompressionBombError + pixel count check
4. Specific exception handling:
   • UnidentifiedImageError - Invalid images
   • DecompressionBombError - Decompression bombs
   • OSError - System errors
   • MemoryError - Memory exhaustion
5. No silent failures: All errors raise ValidationError
6. Security logging: All events logged for monitoring

@andrewtavis I checked the solution by creating a test file and it passed all the test. Kindly review it if find any dicrepancies I'll fix it. Thank you..

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Maintainer Checklist

The following is a checklist for maintainers to make sure this process goes as well as possible. Feel free to address the points below yourself in further commits if you realize that actions are needed :)

• [ ] The TypeScript, pytest and formatting workflows within the PR checks do not indicate new errors in the files changed

• [ ] The Playwright end to end and Zap penetration tests have been ran and are passing (if necessary)

• [ ] The changelog has been updated with a description of the changes for the upcoming release and the corresponding issue (if necessary)