Fix request sync duplicate public messages (#707)

Co-authored-by: CC <cc@ggg.local>

app/src/test/kotlin/com/bitchat/android/services/AppStateStoreTest.kt

@@ -0,0 +1,58 @@
+package com.bitchat.android.services
+
+import com.bitchat.android.model.BitchatMessage
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+import java.util.Date
+
+class AppStateStoreTest {
+    @Before
+    fun setUp() {
+        AppStateStore.clear()
+    }
+
+    @After
+    fun tearDown() {
+        AppStateStore.clear()
+    }
+
+    @Test
+    fun `public timeline collapses request sync replay even when android message ids differ`() {
+        val timestamp = Date(1_700_000_000_000L)
+        val originalDelivery = BitchatMessage(
+            id = "random-id-from-first-delivery",
+            sender = "alice",
+            content = "hello from sync",
+            timestamp = timestamp,
+            senderPeerID = "1122334455667788"
+        )
+        val requestSyncReplay = originalDelivery.copy(id = "different-random-id-from-replay")
+
+        AppStateStore.addPublicMessage(originalDelivery)
+        AppStateStore.addPublicMessage(requestSyncReplay)
+
+        assertEquals(listOf(originalDelivery), AppStateStore.publicMessages.value)
+    }
+
+    @Test
+    fun `public timeline still keeps same content sent at different packet timestamps`() {
+        val first = BitchatMessage(
+            id = "first-packet-id",
+            sender = "alice",
+            content = "same text",
+            timestamp = Date(1_700_000_000_000L),
+            senderPeerID = "1122334455667788"
+        )
+        val second = first.copy(
+            id = "second-packet-id",
+            timestamp = Date(first.timestamp.time + 1_000L)
+        )
+
+        AppStateStore.addPublicMessage(first)
+        AppStateStore.addPublicMessage(second)
+
+        assertEquals(listOf(first, second), AppStateStore.publicMessages.value)
+    }
+}