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>

app/src/main/java/com/m57/hermescontrol/Navigation.kt

@@ -54,6 +54,7 @@ import com.m57.hermescontrol.theme.LocalHermesStatusColors
 import kotlinx.coroutines.launch
 import com.m57.hermescontrol.ui.authlogin.AuthLoginScreen as AuthLoginScreenContent
 import com.m57.hermescontrol.ui.landing.LandingScreen as LandingScreenContent
+import com.m57.hermescontrol.ui.pairing.PairingCodeEntryScreen as PairingCodeEntryScreenContent
 
 private fun resolveBottomNavItems(names: List<String>): List<ScreenDefinition> =
     names.mapNotNull { name -> ScreenRegistry.ALL_SCREENS.firstOrNull { it.key::class.simpleName == name } }
@@ -70,7 +71,7 @@ private fun appEntryProvider(
                 NavigationController.backStack?.add(AuthLoginScreen)
             },
             onPairingLogin = {
-                NavigationController.backStack?.add(PairingScreen)
+                NavigationController.backStack?.add(PairingCodeEntryScreen)
             },
         )
     }
@@ -86,6 +87,17 @@ private fun appEntryProvider(
         )
     }
 
+    entry<PairingCodeEntryScreen> {
+        PairingCodeEntryScreenContent(
+            onConnected = {
+                NavigationController.resetTo(ChatScreen)
+            },
+            onBack = {
+                NavigationController.goBack()
+            },
+        )
+    }
+
     ScreenRegistry.ALL_SCREENS.forEach { screen ->
         addEntryProvider(clazz = screen.key::class) {
             screen.content(sessionId, openDrawer)
@@ -123,7 +135,8 @@ fun MainNavigation(sessionId: String? = null) {
 
     val showBottomBar =
         currentScreen != LandingScreen &&
-            currentScreen != AuthLoginScreen
+            currentScreen != AuthLoginScreen &&
+            currentScreen != PairingCodeEntryScreen
     val gesturesEnabled = currentScreen in DRAWER_GESTURE_SCREENS
     val openDrawer: () -> Unit = { scope.launch { drawerState.open() } }