fix: chunk large cached events to avoid Preferences 8KB limit on desktop

java.util.prefs.Preferences (desktop Settings backend) has an 8KB
per-value limit. Schedule JSON exceeds this. Now splits into 8000-char
chunks stored as cached_events_chunk_<account>_<i>, with a count key.
Maintains backward compat with old single-value format.

composeApp/src/commonMain/kotlin/ch/parano/myice/cache/ScheduleCache.kt

@@ -9,10 +9,16 @@ import kotlinx.serialization.json.Json
 
 class ScheduleCache(private val settings: Settings) {
 
+    companion object {
+        private const val CHUNK_SIZE = 8000
+    }
+
     private val json = Json { ignoreUnknownKeys = true }
     private val eventListSerializer = ListSerializer(Event.serializer())
 
     private fun eventsKey(account: String) = "cached_events_$account"
+    private fun eventsChunkCountKey(account: String) = "cached_events_count_$account"
+    private fun eventsChunkKey(account: String, index: Int) = "cached_events_chunk_${account}_$index"
     private fun agegroupKey(account: String) = "filters_agegroup_$account"
     private fun subgroupKey(account: String) = "filters_subgroup_$account"
     private fun typeFilterKey(account: String) = "filters_typefilter_$account"
@@ -20,11 +26,31 @@ class ScheduleCache(private val settings: Settings) {
 
     @OptIn(ExperimentalTime::class)
     fun saveEvents(account: String, events: List<Event>) {
-        settings.putString(eventsKey(account), json.encodeToString(eventListSerializer, events))
+        val jsonStr = json.encodeToString(eventListSerializer, events)
+        val chunks = jsonStr.chunked(CHUNK_SIZE)
+
+        settings.remove(eventsKey(account))
+        settings.putInt(eventsChunkCountKey(account), chunks.size)
+        chunks.forEachIndexed { i, chunk ->
+            settings.putString(eventsChunkKey(account, i), chunk)
+        }
         settings.putLong(timestampKey(account), Clock.System.now().toEpochMilliseconds())
     }
 
     fun loadEvents(account: String): List<Event>? {
+        val chunkCount = settings.getIntOrNull(eventsChunkCountKey(account))
+        if (chunkCount != null && chunkCount > 0) {
+            val jsonStr = (0 until chunkCount).mapNotNull { i ->
+                settings.getStringOrNull(eventsChunkKey(account, i))
+            }.joinToString("")
+            if (jsonStr.isEmpty()) return null
+            return try {
+                json.decodeFromString(eventListSerializer, jsonStr)
+            } catch (e: Exception) {
+                null
+            }
+        }
+
         val jsonString = settings.getStringOrNull(eventsKey(account)) ?: return null
         return try {
             json.decodeFromString(eventListSerializer, jsonString)
@@ -58,6 +84,11 @@ class ScheduleCache(private val settings: Settings) {
     }
 
     fun clearCache(account: String) {
+        val chunkCount = settings.getIntOrNull(eventsChunkCountKey(account)) ?: 0
+        for (i in 0 until chunkCount) {
+            settings.remove(eventsChunkKey(account, i))
+        }
+        settings.remove(eventsChunkCountKey(account))
         settings.remove(eventsKey(account))
         settings.remove(timestampKey(account))
         settings.remove(agegroupKey(account))