Modernize codebase: C++17, remove Tor v2, add embedded Tor scaffold, IBD speedups

- Replace ~290 BOOST_FOREACH with C++11 range-for across 41+ files
- Replace boost::assign::map_list_of with C++11 brace initialization
- Remove PAIRTYPE macro (no longer needed without BOOST_FOREACH)
- Guard OpenSSL locking callbacks for 3.x (no-ops in >= 1.1.0)
- Fix Qt deprecated APIs for Qt6 compat (QStyleOptionViewItemV4, setResizeMode)
- Add openssl_compat.h version string wrapper
- Enable C++17 in makefile.unix and triangles-qt.pro

- Delete 163 dead Tor v2 source files (~150K lines removed)
- Add embedded Tor scaffold (tor_embedded.h/cpp) using tor_api.h
- Add build-libtor.sh helper and CODEX-TOR-GUIDE.md
- Update makefile.unix and .pro with USE_TOR_EMBEDDED optional flag
- Fallback to external tor_process when not compiled with libtor

- IBD pipeline refill: 100 -> 1000 blocks
- Send/recv buffer limits: unlimited -> 100MB/32MB
- Orphan block cap: unlimited -> 750 with random eviction
- Socket poll: 10ms -> 1ms during IBD
- Message handler sleep: 10ms -> 1ms during IBD
- Stall detection timeout: 5s -> 2s

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/walletdb.cpp

@@ -61,7 +61,7 @@ int64_t CWalletDB::GetAccountCreditDebit(const string& strAccount)
     ListAccountCreditDebit(strAccount, entries);
 
     int64_t nCreditDebit = 0;
-    BOOST_FOREACH (const CAccountingEntry& entry, entries)
+    for (const CAccountingEntry& entry : entries)
         nCreditDebit += entry.nCreditDebit;
 
     return nCreditDebit;
@@ -130,7 +130,7 @@ CWalletDB::ReorderTransactions(CWallet* pwallet)
     }
     list<CAccountingEntry> acentries;
     ListAccountCreditDebit("", acentries);
-    BOOST_FOREACH(CAccountingEntry& entry, acentries)
+    for (CAccountingEntry& entry : acentries)
     {
         txByTime.insert(make_pair(entry.nTime, TxPair((CWalletTx*)0, &entry)));
     }
@@ -157,7 +157,7 @@ CWalletDB::ReorderTransactions(CWallet* pwallet)
         else
         {
             int64_t nOrderPosOff = 0;
-            BOOST_FOREACH(const int64_t& nOffsetStart, nOrderPosOffsets)
+            for (const int64_t& nOffsetStart : nOrderPosOffsets)
             {
                 if (nOrderPos >= nOffsetStart)
                     ++nOrderPosOff;
@@ -515,7 +515,7 @@ DBErrors CWalletDB::LoadWallet(CWallet* pwallet)
         pwallet->nTimeFirstKey = 1; // 0 would be considered 'no value'
 
 
-    BOOST_FOREACH(uint256 hash, wss.vWalletUpgrade)
+    for (uint256 hash : wss.vWalletUpgrade)
         WriteTx(hash, pwallet->mapWallet[hash]);
 
     // Rewrite encrypted wallets of versions 0.4.0 and 0.5.0rc:
@@ -684,7 +684,7 @@ bool CWalletDB::Recover(CDBEnv& dbenv, std::string filename, bool fOnlyKeys)
     CWalletScanState wss;
 
     DbTxn* ptxn = dbenv.TxnBegin();
-    BOOST_FOREACH(CDBEnv::KeyValPair& row, salvagedData)
+    for (CDBEnv::KeyValPair& row : salvagedData)
     {
         if (fOnlyKeys)
         {