ImportScreen: shadow fades out over last 80px of scroll

shadowAlpha = (remaining / 80).coerceIn(0,1) — full strength when
far from bottom, smoothly fades to zero over the last 80px.

src/main/kotlin/com/bolenpad/photophetch/ui/ImportScreen.kt

@@ -48,24 +48,32 @@ fun ImportScreen(state: AppState) {
 
         // ── Scrollable body with bottom shadow indicator ─────────────────────
         val scrollState = rememberScrollState()
-        val showShadow by remember { derivedStateOf { scrollState.value < scrollState.maxValue } }
+        // shadowAlpha: 1.0 when far from bottom, fades to 0.0 over the last 80px
+        val shadowAlpha by remember {
+            derivedStateOf {
+                val remaining = scrollState.maxValue - scrollState.value
+                (remaining / 80f).coerceIn(0f, 1f)
+            }
+        }
 
         Box(
             modifier = Modifier
                 .weight(1f)
-                .then(
-                    if (showShadow) Modifier.drawWithContent {
+                .drawWithContent {
                     drawContent()
-                        // Thin shadow strip along the bottom edge
+                    if (shadowAlpha > 0f) {
                         drawRect(
                             brush = Brush.verticalGradient(
-                                colors = listOf(Color.Transparent, Color.Black.copy(alpha = 0.10f)),
+                                colors = listOf(
+                                    Color.Transparent,
+                                    Color.Black.copy(alpha = 0.10f * shadowAlpha),
+                                ),
                                 startY = size.height - 24.dp.toPx(),
                                 endY = size.height,
                             )
                         )
-                    } else Modifier
-                )
+                    }
+                }
         ) {
             Column(
                 modifier = Modifier