(Open Prices) Proof Addition

[teolemon]

• Price proof: convert images to webp before upload ? #5952

### Add receipts
- [ ] https://github.com/openfoodfacts/smooth-app/issues/5204
- [ ] https://github.com/openfoodfacts/smooth-app/issues/5208
- [ ] https://github.com/openfoodfacts/smooth-app/issues/5209

### Proof addition + ML magic
- [ ] Create a shared system to analyse EXIF data from the photos (camera AND/OR gallery), extracting date and coordinates
- [ ] Create a system to fetch store candidates based on coordinates (we probably need a new server route)
- [ ] https://github.com/openfoodfacts/smooth-app/issues/5202
- [ ] Add a system to attempt extracting prices from the above generated cards (using MLKIT OCR ?)
- [ ] Add a system to crop an aisle panorama into individual prices for the 'Add multiple products' below. Consider asking for a new server route to upload crop coordinates instead of multiple crops of the same image
- [x] Add a client side system to add black resizeable squares on device to preserve privacy of receipts
- [ ] Add a client side system to extract prices and items from receipts (using MLKIT OCR ?)
- [ ] Port the contribution assistant to the mobile app, hidden in DEV
- [ ] https://github.com/openfoodfacts/smooth-app/issues/6010