Four wins:
1. Replace <input type=file capture> with a getUserMedia
viewfinder modal on mobile. Tapping the shutter goes straight
to the crop modal — skips the OS "retake/use" confirm step.
Falls back to file picker if camera permission is denied or
the API is unavailable. "Pick from file" icon
(photo_library) inside the camera modal opens the gallery
on demand.
2. Drop the Reset button — with no default crop box, "reset" is
just "no box again," which is the starting state anyway.
3. The check (Use this) button is now larger and more prominent
— wider padding, 24px icon, accent fill.
4. Invert-colours toggle (invert_colors icon) in the crop modal.
White-on-dark text (signs, menus, screenshots) breaks
Tesseract because the binariser was made for ink on paper.
Toggling the button flips the grayscale buffer before
adaptive thresholding so the binary output ends up
black-on-white. State plumbed cleanly: openCropper now
resolves with {blob, invert}; preprocessForOCR takes an
{invert} option; binarizeAdaptive applies the flip.
Also: drop `capture=environment` from the file <input>. Without
it the file path correctly opens the gallery/file dialog instead
of re-opening the OS camera when the user picks "Pick from file".
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