add fee-aware mining, coinbase validation, and reorg-safe orphan handling

Mining: blocks now include mempool txs, select spendable txs by fee, and pay coinbase as base reward + fees in main.c.
 - Consensus: block validation now enforces coinbase accounting and rejects invalid coinbase placement, including coinbase on amount2, in block.c and transaction.c.
 - Chain state: rollback now rebuilds currentSupply/currentReward, and block addition preflights spendability before mutating balances in chain.c.
 - Orphans/reorgs: orphan retry is safer, rollback-triggered sync reattaches orphans immediately, and transient orphan failures no longer drop blocks in orphan_pool.c and main.c.
 - Networking/mempool: node lifecycle now initializes the mempool, broadcasts can exclude one peer, and mempool snapshotting supports mining selection in net_node.c and txmempool.c.
 - Ledger simulation: added non-mutating spendable-transaction selection for block assembly in balance_sheet.c.

include/balance_sheet.h

@@ -8,6 +8,7 @@
 #include <stdio.h>
 #include <khash/khash.h>
 #include <crypto/crypto.h>
+#include <block/transaction.h>
 #include <string.h>
 #include <utils.h>
 #include <uint256.h>
@@ -29,4 +30,12 @@ bool BalanceSheet_LoadFromFile(const char* inPath);
 void BalanceSheet_Print();
 void BalanceSheet_Destroy();
 
+bool BalanceSheet_SelectSpendableTransactions(
+    const signed_transaction_t* candidates,
+    size_t candidateCount,
+    signed_transaction_t** outAccepted,
+    size_t* outAcceptedCount,
+    uint64_t* outTotalFees
+);
+
 #endif

include/block/block.h

@@ -36,6 +36,7 @@ void Block_AddTransaction(block_t* block, signed_transaction_t* tx);
 void Block_RemoveTransaction(block_t* block, uint8_t* txHash);
 bool Block_HasValidProofOfWork(const block_t* block);
 bool Block_AllTransactionsValid(const block_t* block);
+bool Block_ValidateCoinbaseAndFees(const block_t* block, uint64_t expectedCoinbaseAmount, uint64_t* outTotalFees);
 bool Block_IsFullyValid(const block_t* block);
 void Block_ShutdownPowContext(void);
 void Block_Destroy(block_t* block);

include/nets/net_node.h

@@ -57,7 +57,7 @@ int Node_ConnectPeer(net_node_t* node, const char* ip, unsigned short port);
 int Node_ConnectStartupPeers(net_node_t* node, const char** ips, const unsigned short* ports, size_t peersCount);
 
 int Node_SendPacket(net_node_t* node, tcp_connection_t* conn, packet_type_t packetType, const void* payload, size_t payloadLen);
-int Node_BroadcastTransaction(net_node_t* node, signed_transaction_t* tx);
+int Node_BroadcastTransaction(net_node_t* node, signed_transaction_t* tx, tcp_connection_t* excludeNode);
 
 // Helpers for outbound peer selection and block broadcast
 int Node_GetBestOutboundPeer(net_node_t* node, tcp_connection_t** outConn, uint64_t* outHeight);

include/txmempool.h

@@ -13,6 +13,7 @@ void TxMempool_Init();
 // Assumed that the transation was confirmed to be valid
 int TxMempool_Insert(signed_transaction_t tx);
 bool TxMempool_Lookup(uint8_t* txHash, signed_transaction_t* out);
+bool TxMempool_Snapshot(signed_transaction_t** outTxs, size_t* outCount);
 void TxMempool_Print();
 void TxMempool_Destroy();