fix(components): match full-screen picker bar icons to the runtime theme

A Compose Dialog owns its own Window whose status/navigation-bar icon
appearance is seeded from the XML theme, not from the host activity's
runtime edge-to-edge state. With decorFitsSystemWindows = false the
FullScreenPicker draws under the bars, exposing icons that don't match
the active theme — dark icons on a dark picker (near-invisible), and the
mirror-image nav-bar bug in light theme.

Expose the resolved light/dark decision from FloretExpressiveTheme as
LocalFloretDarkTheme and drive the dialog window's
isAppearanceLight{Status,Navigation}Bars from it, so the appearance
tracks the in-app light/dark choice even when it diverges from the
system night resource qualifier.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/Theme.kt

@@ -10,8 +10,19 @@ import androidx.compose.material3.Typography
 import androidx.compose.material3.dynamicDarkColorScheme
 import androidx.compose.material3.dynamicLightColorScheme
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.staticCompositionLocalOf
 import androidx.compose.ui.platform.LocalContext
 
+/**
+ * The resolved light/dark decision the current [FloretExpressiveTheme] is running
+ * with, carried down the tree so components can align window chrome (e.g. status-
+ * and navigation-bar icon appearance) with the *runtime* theme rather than the
+ * system night resource qualifier — the two diverge whenever an app overrides
+ * light/dark from settings. Defaults to `false` (light) outside a Floret theme.
+ */
+val LocalFloretDarkTheme = staticCompositionLocalOf { false }
+
 /**
  * The family's Material 3 Expressive theme factory. Honours system light/dark
  * and Material You dynamic colour (API 31+), falling back to the app-supplied
@@ -43,10 +54,12 @@ fun FloretExpressiveTheme(
         else -> lightScheme
     }
 
-    MaterialExpressiveTheme(
-        colorScheme = colorScheme,
-        typography = typography,
-        motionScheme = MotionScheme.standard(),
-        content = content,
-    )
+    CompositionLocalProvider(LocalFloretDarkTheme provides darkTheme) {
+        MaterialExpressiveTheme(
+            colorScheme = colorScheme,
+            typography = typography,
+            motionScheme = MotionScheme.standard(),
+            content = content,
+        )
+    }
 }