StoreForwardModule::historyAdd: memcpy source size, not buffer capacity (#10250)

`memcpy(... p.payload.bytes, meshtastic_Constants_DATA_PAYLOAD_LEN)`
reads past the actual payload when the incoming packet's payload is
shorter than `DATA_PAYLOAD_LEN` (237 bytes). The code just above
already records the correct size:

    this->packetHistory[...].payload_size = p.payload.size;

but then the memcpy ignores that and copies the full buffer capacity,
pulling uninitialized / adjacent memory bytes into the history entry.
Those extra bytes are later rebroadcast whenever the Store & Forward
module replays the packet.

Fix: memcpy using `p.payload.size` (the actual payload length) instead
of the constant buffer capacity.

Classification: bounded out-of-bounds READ into the protobuf scratch
buffer. Not directly exploitable for RCE (the destination buffer is
also DATA_PAYLOAD_LEN), but leaks adjacent memory into replayed
packets and is a latent correctness bug.

src/modules/StoreForwardModule.cpp

@@ -206,7 +206,7 @@ void StoreForwardModule::historyAdd(const meshtastic_MeshPacket &mp)
     this->packetHistory[this->packetHistoryTotalCount].hop_limit = mp.hop_limit;
     this->packetHistory[this->packetHistoryTotalCount].via_mqtt = mp.via_mqtt;
     this->packetHistory[this->packetHistoryTotalCount].transport_mechanism = mp.transport_mechanism;
-    memcpy(this->packetHistory[this->packetHistoryTotalCount].payload, p.payload.bytes, meshtastic_Constants_DATA_PAYLOAD_LEN);
+    memcpy(this->packetHistory[this->packetHistoryTotalCount].payload, p.payload.bytes, p.payload.size);
 
     this->packetHistoryTotalCount++;
 }