feat(upgrade): Merge upgrade screen mascot and preamble into one hero card

Adds UpgradeHeroCard, which pairs the mascot with the preamble copy inside a
single ElevatedCard and stacks them once the copy runs out of room. Used by
the FOSS pitch view and the GPLAY acquisition view; grace episodes and the
FOSS status views keep their standalone header, which has no preamble to
pair with. Screen tests pin the hero's presence and absence per state.

app/src/foss/java/eu/darken/capod/common/upgrade/ui/UpgradeScreen.kt

@@ -156,11 +156,7 @@ private fun UpgradePitchContent(
     UpgradeScreenContent(
         paddingValues = paddingValues,
     ) {
-        UpgradeHeader(
-            mascotSize = 104.dp,
-        )
-
-        UpgradePreambleCard(
+        UpgradeHeroCard(
             text = stringResource(R.string.upgrade_foss_preamble),
             colors = CardDefaults.elevatedCardColors(
                 containerColor = MaterialTheme.colorScheme.primaryContainer,