feat(android): the launch screen shows the padlock, not Delphi's flame

The launcher icon and the launch screen are different resources. On Android 12+ the theme points windowSplashScreenAnimatedIcon at splash_vector, which was Delphi's logo, over a #FFF background - a white flash before a dark app, every single launch.

Same padlock, drawn at 288 units with its content inside the central 192 the system guarantees. splash_background goes slate, in the light variant too since the app has only one theme. For Android 11 and earlier, which have no SplashScreen API and merely paint windowBackground, splash_image_def composes the background and the logo itself.

One source for the vector, copied onto the density and night variants by repack: four identical files in the repo would eventually diverge.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

android-client/android-res/values/colors.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Remplace le colors.xml genere, dont splash_background vaut #FFF : un
+     ecran de demarrage blanc suivi d'une application sombre donne un flash
+     desagreable a chaque lancement. -->
+<resources xmlns:android="http://schemas.android.com/apk/res/android">
+    <color name="splash_background">#0F172A</color>
+</resources>