feat(learn,train,todo,meditate): the icons on a white tile again, coloured by the system's theme on Android and iOS (ADR 0031, D9, D10)

D10 returns every icon to D1's white tile, D8's dark one undone, the
gradients as D5 gives them (cobalt holds about 5.7 : 1 against white).

D9 adds the variants the systems colour by their theme, all from the same
glyph at the same place, drawn by tool/app_icons.py and written into the
projects by flutter_launcher_icons: Android's monochrome layer, which
themed icons tint (Android 13 and later), and iOS's dark and tinted icons
(iOS 18 and later), the dark one keeping D8's lift of 30 % towards white
on iOS's own dark background. macOS needs an Icon Composer file made on a
Mac and keeps the plain icon until then.

Whats-New: The app's icon is white again, and takes the system's colours where Android or iOS themes its icons.
Whats-New-De: Das App-Symbol ist wieder weiß und nimmt die Farben des Systems an, wo Android oder iOS seine Symbole einfärbt.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_flutter/android/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -6,4 +6,9 @@
           android:drawable="@drawable/ic_launcher_foreground"
           android:inset="16%" />
   </foreground>
+  <monochrome>
+      <inset
+          android:drawable="@drawable/ic_launcher_monochrome"
+          android:inset="16%" />
+  </monochrome>
 </adaptive-icon>

apps/learn/halkyon_learn_flutter/android/app/src/main/res/values/colors.xml

@@ -1,4 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <color name="ic_launcher_background">#131520</color>
+    <color name="ic_launcher_background">#ffffff</color>
 </resources>