vc=33 fix: add FeedCacheStore.kt to git

git commit -am only stages tracked files. The new file existed locally
but wasn't in the previous commit; build failed with Unresolved
reference 'FeedCache' on every site that used it.

strawApp/src/main/kotlin/com/sulkta/straw/data/FeedCacheStore.kt

@@ -0,0 +1,71 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Sulkta-Coop
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ * Persistent per-channel cache for the subscription feed. Survives
+ * process death, so opening Subs after a cold start shows the last
+ * successful fetch immediately instead of waiting 5+ seconds for 30
+ * channel browses to resolve.
+ *
+ * Storage: SharedPreferences with a single JSON blob. Total payload is
+ * small (30 subs * 30 items * ~250 bytes = ~225 KB), well within SP's
+ * comfortable size and well below the multi-MB threshold where you'd
+ * want to graduate to Room or a file.
+ *
+ * Concurrency: writes from the feed VM are debounced via the single
+ * `persist` call inside fetchChannelInto's success path. Reads happen
+ * on VM init and are synchronous.
+ */
+
+package com.sulkta.straw.data
+
+import android.content.Context
+import android.content.SharedPreferences
+import com.sulkta.straw.feature.search.StreamItem
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+
+@Serializable
+data class FeedCacheEntry(
+    val fetchedAt: Long,
+    val items: List<StreamItem>,
+)
+
+private const val PREFS = "straw_feed_cache"
+private const val KEY = "cache_v1"
+
+class FeedCacheStore(context: Context) {
+    private val sp: SharedPreferences = context.getSharedPreferences(PREFS, Context.MODE_PRIVATE)
+    private val json = Json { ignoreUnknownKeys = true; isLenient = true }
+
+    /** Snapshot of the disk cache. Returns empty map if nothing saved. */
+    fun load(): Map<String, FeedCacheEntry> = runCatching {
+        val s = sp.getString(KEY, null) ?: return emptyMap()
+        json.decodeFromString<Map<String, FeedCacheEntry>>(s)
+    }.getOrDefault(emptyMap())
+
+    /** Atomic write. Caller is responsible for diffing if needed. */
+    fun save(map: Map<String, FeedCacheEntry>) {
+        val s = json.encodeToString(map)
+        sp.edit().putString(KEY, s).apply()
+    }
+
+    fun clear() {
+        sp.edit().remove(KEY).apply()
+    }
+}
+
+object FeedCache {
+    @Volatile private var instance: FeedCacheStore? = null
+
+    fun init(context: Context) {
+        if (instance == null) {
+            synchronized(this) {
+                if (instance == null) instance = FeedCacheStore(context.applicationContext)
+            }
+        }
+    }
+
+    fun get(): FeedCacheStore = instance
+        ?: error("FeedCacheStore not initialized — call FeedCache.init(context)")
+}