feat(#350): pairing login flow with QR scan + manual entry (#421)

* feat(#350): pairing login flow with QR scan + manual entry

Adds PairingCodeEntryScreen with CameraX + ML Kit QR scanning
and manual code entry. The screen parses hermes://connect URIs,
Base64-encoded JSON, and raw token formats, validates via
/api/status, and saves credentials on success.

- New PairingCodeEntryScreen + PairingCodeEntryViewModel
- CameraX 1.4.1 + ML Kit barcode-scanning 17.3.0
- CAMERA permission + proguard rules
- Landing screen Pairing Login button wired correctly

* fix(#350): resolve smart-cast on delegated property for errorMessage

Co-authored-by: Hy4ri <hy4ri@users.noreply.github.com>

* refactor(#421): remove QR scanner from pairing login

- Remove CameraX + ML Kit barcode dependencies
- Drop CAMERA permission and camera feature from manifest
- Strip QrScannerTab, QrCodeScannerView, processFrame composables
- Remove camera permission state/methods from ViewModel
- Purge all QR/camera strings from strings.xml
- Delete ML Kit proguard rules

The pairing login now shows only the manual code entry UI.

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

gradle/libs.versions.toml

@@ -79,7 +79,6 @@ sqlcipher = { module = "net.zetetic:sqlcipher-android", version.ref = "sqlcipher
 # Image loading
 coil-compose = { module = "io.coil-kt:coil-compose", version.ref = "coil" }
 
-
 [plugins]
 android-application = { id = "com.android.application", version.ref = "androidGradlePlugin" }
 compose-compiler = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }