feat(upload): strip EXIF metadata from uploaded images

[singhanurag0317-bit]

Feature: Automatic EXIF Metadata Stripping for Uploaded Images

Closes #1657

Problem

Uploaded user photos could retain sensitive EXIF metadata (GPS coordinates, camera serial numbers, timestamps), violating user privacy.

Change

• New stripImageExifData(filePath) in backend/src/middleware/upload.middleware.js:
  • Re-encodes the image through a sharp pipeline (.rotate() bakes EXIF orientation into pixels, then output is written without metadata), removing all EXIF/GPS/camera data while keeping the image visually identical.
  • Reads via buffer to avoid platform file-handle quirks.
• validateImageChain now runs stripImageExifData as a step in the upload validation pipeline, so every single-file upload is scrubbed of EXIF prior to storage/processing. On failure the file is cleaned up and a 400 is returned.

Tests

New backend/src/middleware/__tests__/stripExif.test.js:

• JPEG created with withMetadata({ orientation: 6 }) has EXIF + orientation removed after stripping.
• Stripped JPEG stays valid, same orientation-baked dimensions (300x400), still jpeg.
• PNG files are stripped too.

Full backend suite: 9 suites / 23 tests passing.

[vercel]

@singhanurag0317-bit is attempting to deploy a commit to the souma9830's projects Team on Vercel.

A member of the Team first needs to authorize it.