fix(avatar): center-crop profile picture thumbnails to prevent squashing

The profile picture thumbnail cache pre-resized every source to a square
256x256 via createScaledBitmap, stretching non-square avatars. The cache
hit path returned the pre-squashed bitmap with isSampled=true, so the
ContentScale.Crop at the composable could not undo it.

Fuses center-crop + scale into a single Bitmap.createBitmap call with a
scale matrix so the cached thumbnail matches the CircleShape +
ContentScale.Crop render contract with one allocation. try/finally
guarantees the source bitmap is recycled even if createBitmap throws.

Bumps the cache subdir to profile_thumbnails_v2 so existing squashed
thumbnails are abandoned and regenerated, and reclaims the orphaned v1
directory on first init.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

amethyst/src/main/java/com/vitorpamplona/amethyst/AppModules.kt

@@ -440,7 +440,9 @@ class AppModules(
     // thumbnail disk cache for profile pictures
     val thumbnailDiskCache: ThumbnailDiskCache by lazy {
         Log.d("AppModules", "ThumbnailDiskCache Init")
-        ThumbnailDiskCache(appContext.safeCacheDir().resolve("profile_thumbnails"))
+        // One-shot reclaim of the v1 cache dir, which held squashed thumbnails.
+        appContext.safeCacheDir().resolve("profile_thumbnails").deleteRecursively()
+        ThumbnailDiskCache(appContext.safeCacheDir().resolve("profile_thumbnails_v2"))
     }
 
     // crash report storage

amethyst/src/main/java/com/vitorpamplona/amethyst/service/images/ThumbnailDiskCache.kt

@@ -22,6 +22,7 @@ package com.vitorpamplona.amethyst.service.images
 
 import android.graphics.Bitmap
 import android.graphics.BitmapFactory
+import android.graphics.Matrix
 import com.vitorpamplona.quartz.nip01Core.core.toHexKey
 import com.vitorpamplona.quartz.utils.Log
 import com.vitorpamplona.quartz.utils.sha256.sha256
@@ -111,9 +112,29 @@ class ThumbnailDiskCache(
                 }
             val decoded = BitmapFactory.decodeFile(path, decodeOptions) ?: return false
 
-            // Scale to exact target size and write atomically
+            // Fuse center-crop + scale into one allocation; matches CircleShape + ContentScale.Crop.
-            val scaled = Bitmap.createScaledBitmap(decoded, targetSize, targetSize, true)
+            val side = minOf(decoded.width, decoded.height)
-            if (scaled !== decoded) decoded.recycle()
+            val scaled =
+                if (decoded.width == targetSize && decoded.height == targetSize) {
+                    decoded
+                } else {
+                    // try/finally ensures decoded is recycled even if createBitmap throws.
+                    try {
+                        val scale = targetSize.toFloat() / side
+                        val matrix = Matrix().apply { setScale(scale, scale) }
+                        Bitmap.createBitmap(
+                            decoded,
+                            (decoded.width - side) / 2,
+                            (decoded.height - side) / 2,
+                            side,
+                            side,
+                            matrix,
+                            true,
+                        )
+                    } finally {
+                        decoded.recycle()
+                    }
+                }
 
             val tempFile = File(cacheDir, "$key.tmp")
             tempFile.outputStream().use { out ->