feat: add custom house launcher icon, themed splash screen, and F-Droid metadata

Replace default Flutter icon with white house on sage green (#7A9A6D) background.
Add native splash screen with themed colors (#F5F0E8 light, #2A2520 dark).
Include F-Droid metadata with screenshots for de-DE and en-US locales.
Add CHANGELOG.md tracking all releases from v1.0.0 to v1.1.3.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

android/app/src/main/res/drawable/launch_background.xml

@@ -1,12 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Modify this file to customize your launch splash screen -->
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:drawable="@android:color/white" />
-
-    <!-- You can insert your own image assets here -->
-    <!-- <item>
-        <bitmap
-            android:gravity="center"
-            android:src="@mipmap/launch_image" />
-    </item> -->
+    <item>
+        <bitmap android:gravity="fill" android:src="@drawable/background"/>
+    </item>
+    <item>
+        <bitmap android:gravity="center" android:src="@drawable/splash"/>
+    </item>
 </layer-list>