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/miner.cpp

@@ -72,7 +72,7 @@ public:
     {
         printf("COrphan(hash=%s, dPriority=%.1f, dFeePerKb=%.1f)\n",
                ptx->GetHash().ToString().substr(0,10).c_str(), dPriority, dFeePerKb);
-        BOOST_FOREACH(uint256 hash, setDependsOn)
+        for (uint256 hash : setDependsOn)
             printf("   setDependsOn %s\n", hash.ToString().substr(0,10).c_str());
     }
 };
@@ -188,7 +188,7 @@ CBlock* CreateNewBlock(CWallet* pwallet, bool fProofOfStake, int64_t* pFees)
             double dPriority = 0;
             int64_t nTotalIn = 0;
             bool fMissingInputs = false;
-            BOOST_FOREACH(const CTxIn& txin, tx.vin)
+            for (const CTxIn& txin : tx.vin)
             {
                 // Read prev transaction
                 CTransaction txPrev;
@@ -335,7 +335,7 @@ CBlock* CreateNewBlock(CWallet* pwallet, bool fProofOfStake, int64_t* pFees)
             uint256 hash = tx.GetHash();
             if (mapDependers.count(hash))
             {
-                BOOST_FOREACH(COrphan* porphan, mapDependers[hash])
+                for (COrphan* porphan : mapDependers[hash])
                 {
                     if (!porphan->setDependsOn.empty())
                     {