feat: Refactor MeshService into smaller, single-responsibility components (#4108)

Signed-off-by: James Rich <2199651+jamesarich@users.noreply.github.com>

app/src/main/java/com/geeksville/mesh/service/MeshDataMapper.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2025 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.geeksville.mesh.service
+
+import org.meshtastic.core.model.DataPacket
+import org.meshtastic.proto.MeshProtos.MeshPacket
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class MeshDataMapper @Inject constructor(private val nodeManager: MeshNodeManager) {
+    fun toNodeID(n: Int): String = if (n == DataPacket.NODENUM_BROADCAST) {
+        DataPacket.ID_BROADCAST
+    } else {
+        nodeManager.nodeDBbyNodeNum[n]?.user?.id ?: DataPacket.nodeNumToDefaultId(n)
+    }
+
+    fun toDataPacket(packet: MeshPacket): DataPacket? = if (!packet.hasDecoded()) {
+        null
+    } else {
+        val data = packet.decoded
+        DataPacket(
+            from = toNodeID(packet.from),
+            to = toNodeID(packet.to),
+            time = packet.rxTime * 1000L,
+            id = packet.id,
+            dataType = data.portnumValue,
+            bytes = data.payload.toByteArray(),
+            hopLimit = packet.hopLimit,
+            channel = if (packet.pkiEncrypted) DataPacket.PKC_CHANNEL_INDEX else packet.channel,
+            wantAck = packet.wantAck,
+            hopStart = packet.hopStart,
+            snr = packet.rxSnr,
+            rssi = packet.rxRssi,
+            replyId = data.replyId,
+            relayNode = packet.relayNode,
+            viaMqtt = packet.viaMqtt,
+        )
+    }
+}