feat(bills): render bills at the app root; drop camera frosting (#1220)

* feat(bills): render bills at the app root; drop camera frosting

Phase B of moving bills out of the scanner. A presented bill now renders at the
app root instead of inside the camera screen, so it appears over ANY screen and
is fully decoupled from the camera.

- New BillOverlay (:shared:bills), mounted at the app root in App.kt next to
  ScrimOverlay. It reads the app-scoped billState via LocalSessionController and
  owns the swipe-to-dismiss gesture, enter/exit animation, tip-modal positioning,
  and the below-bill decorators. Touch-transparent when no bill is present.
- ScannableContainer slims down to camera + HUD: it no longer draws the bill,
  and hides its DecorView HUD while a bill is up (billState.bill != null).
- Remove the frosted tip-card camera backdrop entirely: delete
  TipCardCameraBackdrop, drop the previewView plumbing from Scanner, and render
  TipCard as a solid opaque card (LocalTipCard{Color,BaseAlpha} now default to
  the opaque fallback; the backdrop composition local is gone).

The FrostedTipCard feature flag is now unused (left in place; harmless).

* feat(bills): hide the tab bar while a bill/tip card is presented

Bills render at the app root above everything, so the v2 tab bar would show
beneath a presented bill. Gate AppNavigationBar visibility on the app-scoped
billState (bill == null) so the bar slides out while a bill is up and returns
on dismiss.

* feat(bills): scrim behind the bill (over app content) via the root ScrimController

When a bill/tip card is presented over app content (not the camera), dim and
block the content beneath it so it reads as a focused modal. Drive the shared
root ScrimController (its ScrimOverlay already sits just below BillOverlay), so
it uses the theme scrim colour and gets tap-to-dismiss for free. Skipped on the
scanner tab, where the live camera stays visible behind the bill.

- ScrimController.hide() made public so BillOverlay can conceal the scrim when
  the bill clears itself (e.g. swipe dismiss) without re-invoking onDismiss.

Author: bmc08gt

apps/flipcash/app/build.gradle.kts

@@ -183,6 +183,7 @@ dependencies {
 
     implementation(project(":apps:flipcash:core"))
     implementation(project(":apps:flipcash:shared:accesskey"))
+    implementation(project(":apps:flipcash:shared:bills"))
     implementation(project(":apps:flipcash:shared:analytics"))
     implementation(project(":apps:flipcash:shared:appsettings"))
     implementation(project(":apps:flipcash:shared:appupdates"))

apps/flipcash/app/src/main/kotlin/com/flipcash/app/internal/ui/App.kt

@@ -69,6 +69,7 @@ import com.getcode.navigation.results.rememberNavResultStateRegistry
 import com.getcode.navigation.scenes.ModalBottomSheetSceneStrategy
 import com.getcode.navigation.scrim.LocalScrimController
 import com.getcode.navigation.scrim.ScrimController
+import com.flipcash.app.bills.BillOverlay
 import com.getcode.navigation.scrim.ScrimOverlay
 import com.getcode.theme.CodeTheme
 import com.getcode.ui.biometrics.LocalBiometricsState
@@ -223,6 +224,11 @@ internal fun App(
                                         }
 
                                         ScrimOverlay(scrimController)
+
+                                        // Bills render at the app root (not inside the scanner) so a
+                                        // presented bill appears over any screen. Reads the app-scoped
+                                        // billState via LocalSessionController.
+                                        BillOverlay()
                                     }
 
                                 val emailCodeChannel = LocalEmailCodeChannel.current

apps/flipcash/app/src/main/kotlin/com/flipcash/app/internal/ui/AppNavigationBar.kt

@@ -11,6 +11,7 @@ import androidx.compose.foundation.layout.navigationBarsPadding
 import androidx.compose.foundation.layout.padding
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.dp
@@ -25,9 +26,12 @@ import com.flipcash.app.core.ui.NavigationBar
 import com.flipcash.app.core.ui.rememberNavigationBarState
 import com.flipcash.app.featureflags.FeatureFlag
 import com.flipcash.app.featureflags.LocalFeatureFlags
+import com.flipcash.app.session.LocalSessionController
 import com.getcode.manager.BottomBarManager
 import com.getcode.navigation.core.CodeNavigator
 import com.getcode.theme.CodeTheme
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.map
 
 /**
  * The hoisted v2 navigation bar — root chrome, not owned by any screen. It renders over whichever
@@ -55,13 +59,20 @@ internal fun AppNavigationBar(
     // while one is showing so it sits below the modal instead of floating over it.
     val bottomBarMessages by BottomBarManager.messages.collectAsStateWithLifecycle()
 
+    // A bill/tip card renders at the app root above everything; hide the bar so it doesn't show
+    // beneath the presented bill.
+    val session = LocalSessionController.current
+    val billUp by remember(session) {
+        session?.billState?.map { it.bill != null } ?: flowOf(false)
+    }.collectAsStateWithLifecycle(initialValue = false)
+
     Box(
         modifier = Modifier
             .then(modifier),
         contentAlignment = Alignment.BottomCenter,
     ) {
         AnimatedVisibility(
-            visible = topTab != null && bottomBarMessages.isEmpty(),
+            visible = topTab != null && bottomBarMessages.isEmpty() && !billUp,
             enter = slideInVertically { it } + fadeIn(),
             exit = slideOutVertically { it } + fadeOut(),
         ) {

apps/flipcash/features/scanner/src/main/kotlin/com/flipcash/app/scanner/internal/Scanner.kt

@@ -1,7 +1,6 @@
 package com.flipcash.app.scanner.internal
 
 import android.annotation.SuppressLint
-import androidx.camera.view.PreviewView
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
@@ -64,9 +63,6 @@ internal fun Scanner() {
     var isPinching by remember { mutableStateOf(false) }
     var zoomRatio by remember { mutableFloatStateOf(1f) }
 
-    // Exposed by CodeScanner so the tip card can snapshot the live feed for its blurred backdrop.
-    var previewView by remember { mutableStateOf<PreviewView?>(null) }
-
     LaunchedEffect(biometricsState, previewing) {
         if (previewing == true) {
             focusManager.clearFocus()
@@ -84,7 +80,6 @@ internal fun Scanner() {
         isPaused = isPaused,
         isPinching = isPinching,
         zoomRatio = zoomRatio,
-        previewView = previewView,
         onAction = {
             when (it) {
                 ScannerDecorItem.Give -> {
@@ -116,7 +111,6 @@ internal fun Scanner() {
                     cameraAvailable = true
                     previewing = it
                 },
-                onPreviewViewChanged = { previewView = it },
                 onCodeScanned = { result ->
                     when (result) {
                         is CodeScanResult.QrCode -> {