Mobile image picker: library + camera, not just camera

Removed capture=“environment” from the file input, which previously forced the camera-only prompt on mobile browsers. Now the standard OS picker offers both photo library access and the option to take a new photo, matching the behavior of apps like WhatsApp.

• Dropped capture=“environment” to restore the full file picker.

• Mobile users can now choose existing photos or take new ones.

• Aligns with WhatsApp-style attachment UX.