feat: upgrade NetworkImageCache — disk cache, shared client, crossfade

Shared OkHttpClient via KaizenApi.imageClient (reuses connection pool),
file-based disk cache in cacheDir/img (survives app restart), 32MB
size-based memory limit instead of 50-entry count, Crossfade animation
on image load.

app/src/main/java/dev/kaizen/app/chat/ChatComponents.kt

@@ -62,6 +62,7 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import dev.kaizen.app.net.Attachment
+import dev.kaizen.app.net.KaizenApi
 import dev.kaizen.app.ui.effect.GlassSurface
 import dev.kaizen.app.ui.effect.GlassTiers
 import dev.kaizen.app.ui.effect.KaizenShadows
@@ -80,6 +81,7 @@ import androidx.compose.foundation.Image
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.platform.LocalClipboard
+import androidx.compose.ui.platform.LocalContext
 import dev.kaizen.app.haptics.rememberHaptics
 import androidx.compose.runtime.rememberCoroutineScope
 import kotlinx.coroutines.launch
@@ -90,9 +92,7 @@ import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.text.style.TextOverflow
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
-import okhttp3.OkHttpClient
 import okhttp3.Request
-import java.util.concurrent.TimeUnit
 import dev.kaizen.app.ui.icon.KaizenIcons
 
 @Composable
@@ -951,39 +951,69 @@ private fun StopButton(onClick: () -> Unit) {
 // ── Attachment rendering ────────────────────────────────────────────────────
 
 private object NetworkImageCache {
+    private const val MAX_MEMORY_BYTES = 32 * 1024 * 1024L // 32MB
+    private var currentBytes = 0L
     private val cache = object : LinkedHashMap<String, ImageBitmap>(32, 0.75f, true) {
-        override fun removeEldestEntry(eldest: MutableMap.MutableEntry<String, ImageBitmap>?) = size > 50
+        override fun removeEldestEntry(eldest: MutableMap.MutableEntry<String, ImageBitmap>?) : Boolean {
+            if (currentBytes <= MAX_MEMORY_BYTES) return false
+            val bmp = eldest?.value ?: return false
+            currentBytes -= bmp.width.toLong() * bmp.height * 4
+            return true
+        }
+    }
+
+    private var diskCacheDir: java.io.File? = null
+
+    fun init(context: android.content.Context) {
+        if (diskCacheDir == null) diskCacheDir = java.io.File(context.cacheDir, "img").also { it.mkdirs() }
+    }
+
+    private fun diskFile(url: String): java.io.File? {
+        val dir = diskCacheDir ?: return null
+        val hash = url.hashCode().toUInt().toString(16)
+        return java.io.File(dir, hash)
     }
-    private val client = OkHttpClient.Builder().connectTimeout(15, TimeUnit.SECONDS).readTimeout(30, TimeUnit.SECONDS).build()
 
     suspend fun load(url: String): ImageBitmap? = withContext(Dispatchers.IO) {
         synchronized(cache) { cache[url] }?.let { return@withContext it }
         try {
+            val bytes = diskFile(url)?.takeIf { it.exists() }?.readBytes()
+                ?: run {
                     val req = Request.Builder().url(url).build()
-            client.newCall(req).execute().use { resp ->
+                    KaizenApi.imageClient.newCall(req).execute().use { resp ->
                         if (!resp.isSuccessful) return@withContext null
-                val bytes = resp.body!!.bytes()
+                        resp.body!!.bytes().also { b -> diskFile(url)?.writeBytes(b) }
+                    }
+                }
             val probe = BitmapFactory.Options().apply { inJustDecodeBounds = true }
             BitmapFactory.decodeByteArray(bytes, 0, bytes.size, probe)
             val scale = maxOf(1, maxOf(probe.outWidth, probe.outHeight) / 1536)
             val opts = BitmapFactory.Options().apply { inSampleSize = scale }
             val bmp = BitmapFactory.decodeByteArray(bytes, 0, bytes.size, opts) ?: return@withContext null
-                bmp.asImageBitmap().also { synchronized(cache) { cache[url] = it } }
+            val imgBmp = bmp.asImageBitmap()
+            synchronized(cache) {
+                currentBytes += imgBmp.width.toLong() * imgBmp.height * 4
+                cache[url] = imgBmp
             }
+            imgBmp
         } catch (_: Exception) { null }
     }
 }
 
 @Composable
 private fun NetworkImage(url: String, contentDescription: String?, modifier: Modifier = Modifier, contentScale: ContentScale = ContentScale.Crop) {
+    val context = LocalContext.current
+    LaunchedEffect(Unit) { NetworkImageCache.init(context) }
     var bitmap by remember(url) { mutableStateOf<ImageBitmap?>(null) }
     LaunchedEffect(url) { bitmap = NetworkImageCache.load(url) }
     val bmp = bitmap
-    if (bmp != null) {
+    androidx.compose.animation.Crossfade(targetState = bmp, label = "img") { img ->
-        Image(bitmap = bmp, contentDescription = contentDescription, modifier = modifier, contentScale = contentScale)
+        if (img != null) {
+            Image(bitmap = img, contentDescription = contentDescription, modifier = modifier, contentScale = contentScale)
         } else {
             Box(modifier.fillMaxWidth().height(160.dp).clip(KaizenShapes.xs).background(MaterialTheme.colorScheme.surfaceVariant.copy(alpha = 0.3f)))
         }
+    }
 }
 
 @Composable

app/src/main/java/dev/kaizen/app/net/KaizenApi.kt

@@ -170,6 +170,10 @@ object KaizenApi {
         .readTimeout(0, TimeUnit.SECONDS) // streaming chat — never time out a healthy stream
         .build()
 
+    val imageClient: OkHttpClient = client.newBuilder()
+        .readTimeout(30, TimeUnit.SECONDS)
+        .build()
+
     private val json = Json { ignoreUnknownKeys = true; encodeDefaults = true }
     private val jsonMedia = "application/json".toMediaType()