Add pinch-to-zoom and auto-zoom to the QR scanner

[Merkost]

Add pinch-to-zoom and auto-zoom to the QR scanner

What

Two new opt-in options on ScannerConfig.Builder:

ScannerConfig.build {
  setUsePinchToZoom(true) // default: false — user pinches preview to zoom
  setUseAutoZoom(true)    // default: false — ML Kit zooms automatically for small/distant codes
}

How

• Pinch-to-zoom: camera setup switched from manually built Preview + ImageAnalysis use cases to LifecycleCameraController, which exposes isPinchToZoomEnabled natively.
• Auto-zoom: ML Kit's ZoomSuggestionOptions is attached to BarcodeScannerOptions, with the zoom callback forwarded to LifecycleCameraController.setZoomRatio(...). Max zoom is read from CameraInfo.zoomState once the camera is initialized.

Closes #214.

Behavior changes to be aware of

• Both options default to false — existing apps see no change.
• Tap-to-focus is now always on. (Happy to gate this behind a separate option if you'd prefer.)
• The explicit 1280×720 analysis resolution was removed; LifecycleCameraController picks its own default. ML Kit scanning still works in manual testing.

Test plan

• Run the sample app on a real device.
• Pinch with setUsePinchToZoom(true) → preview zooms.
• Hold a small/distant code with setUseAutoZoom(true) → camera zooms automatically.
• Both flags off → no zoom behavior.
• Torch toggle still shows/hides correctly.
• Front camera still works.

Notes

• Public API change is additive only: two new Builder methods.
• README's Quick Start block should get matching lines — happy to add them if you'd like.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud