fix(assets): resolve Android and iOS resource generation issues

Android build was failing due to missing drawable and mipmap directories
for splash screens and launcher icons. iOS was missing complete asset
catalog structure for app icons and splash screens.

- Create missing Android resource directories (drawable, mipmap-*)
- Add splash screen files to Android drawable directory
- Generate complete set of Android launcher icons
- Create iOS asset catalog structure with proper Contents.json files
- Generate 21 iOS assets (app icons + splash screens) using ImageMagick
- Add resource validation scripts for both platforms
- Enhance Android resource check to auto-create missing directories

NOTE: you need to test this from a fresh clone and after an npm install!

Android build now completes successfully. iOS assets ready for macOS/Xcode
builds. Both platforms have complete resource sets for development.

android/app/src/main/res/values/colors.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="colorPrimary">#3F51B5</color>
+    <color name="colorPrimaryDark">#303F9F</color>
+    <color name="colorAccent">#FF4081</color>
+    <color name="ic_launcher_background">#FFFFFF</color>
+</resources>