Refresh built-in chat wallpaper patterns and scale them for desktop

Replace the six preset patterns with normalized versions (larger,
consistent motif). They are authored large for mobile's high pixel
density, which reads too big and pixelates when downscaled far on
desktop, so desktop loads a separate, smaller image set at its own
scale (about 0.7x of mobile). Downscaling a large source stays crisp;
upscaling a small one is what pixelates, so the shared image resizing
is left untouched.

First of two commits for the new LIGHT/DARK/BLACK wallpaper schemes;
patterns and colors ship together because the colors are tuned to
these patterns.

apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/views/helpers/ChatWallpaper.kt

@@ -24,13 +24,15 @@ import kotlin.math.*
 
 enum class PresetWallpaper(
   val res: ImageResource,
+  val resDesktop: ImageResource,
   val filename: String,
   val scale: Float,
+  val scaleDesktop: Float,
   val background: Map<DefaultTheme, Color>,
   val tint: Map<DefaultTheme, Color>,
   val colors: Map<DefaultTheme, ThemeColors>,
 ) {
-  CATS(MR.images.wallpaper_cats, "cats", 0.63f,
+  CATS(MR.images.wallpaper_cats, MR.images.wallpaper_cats_desktop, "cats", 0.5f, 0.8f,
     wallpaperBackgrounds(light = "#ffF8F6EA"),
     tint = mapOf(
       DefaultTheme.LIGHT to "#ffefdca6".colorFromReadableHex(),
@@ -65,7 +67,7 @@ enum class PresetWallpaper(
       ),
     )
   ),
-  FLOWERS(MR.images.wallpaper_flowers, "flowers", 0.53f,
+  FLOWERS(MR.images.wallpaper_flowers, MR.images.wallpaper_flowers_desktop, "flowers", 0.5f, 0.8f,
     wallpaperBackgrounds(light = "#ffE2FFE4"),
     tint = mapOf(
       DefaultTheme.LIGHT to "#ff9CEA59".colorFromReadableHex(),
@@ -100,7 +102,7 @@ enum class PresetWallpaper(
       ),
     )
   ),
-  HEARTS(MR.images.wallpaper_hearts, "hearts", 0.59f,
+  HEARTS(MR.images.wallpaper_hearts, MR.images.wallpaper_hearts_desktop, "hearts", 0.5f, 0.8f,
     wallpaperBackgrounds(light = "#ffFDECEC"),
     tint = mapOf(
       DefaultTheme.LIGHT to "#fffde0e0".colorFromReadableHex(),
@@ -135,7 +137,7 @@ enum class PresetWallpaper(
       ),
     )
   ),
-  KIDS(MR.images.wallpaper_kids, "kids", 0.53f,
+  KIDS(MR.images.wallpaper_kids, MR.images.wallpaper_kids_desktop, "kids", 0.5f, 0.8f,
     wallpaperBackgrounds(light = "#ffdbfdfb"),
     tint = mapOf(
       DefaultTheme.LIGHT to "#ffadeffc".colorFromReadableHex(),
@@ -170,7 +172,7 @@ enum class PresetWallpaper(
       ),
     )
   ),
-  SCHOOL(MR.images.wallpaper_school, "school", 0.53f,
+  SCHOOL(MR.images.wallpaper_school, MR.images.wallpaper_school_desktop, "school", 0.5f, 0.8f,
     wallpaperBackgrounds(light = "#ffE7F5FF"),
     tint = mapOf(
       DefaultTheme.LIGHT to "#ffCEEBFF".colorFromReadableHex(),
@@ -205,7 +207,7 @@ enum class PresetWallpaper(
       ),
     )
   ),
-  TRAVEL(MR.images.wallpaper_travel, "travel", 0.68f,
+  TRAVEL(MR.images.wallpaper_travel, MR.images.wallpaper_travel_desktop, "travel", 0.5f, 0.8f,
     wallpaperBackgrounds(light = "#fff9eeff"),
     tint = mapOf(
       DefaultTheme.LIGHT to "#ffeedbfe".colorFromReadableHex(),
@@ -282,7 +284,7 @@ sealed class WallpaperType {
       cachedImages[filename]
     } else {
       val res = if (this is Preset) {
-        (PresetWallpaper.from(filename) ?: PresetWallpaper.CATS).res.toComposeImageBitmap()!!
+        (PresetWallpaper.from(filename) ?: PresetWallpaper.CATS).let { if (appPlatform.isAndroid) it.res else it.resDesktop }.toComposeImageBitmap()!!
       } else {
         try {
           // In case of unintentional image deletion don't crash the app
@@ -308,7 +310,8 @@ sealed class WallpaperType {
     val filename: String,
     override val scale: Float?,
   ): WallpaperType() {
-    val predefinedImageScale = PresetWallpaper.from(filename)?.scale ?: 1f
+    // Desktop shows the pattern smaller than mobile; the large source is downscaled, which stays crisp (upscaling is what pixelates).
+    val predefinedImageScale = PresetWallpaper.from(filename)?.let { if (appPlatform.isAndroid) it.scale else it.scaleDesktop } ?: 1f
   }
 
   data class Image(