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/test/script_tests.cpp

@@ -5,7 +5,6 @@
 #include <boost/algorithm/string/predicate.hpp>
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/algorithm/string/split.hpp>
-#include <boost/foreach.hpp>
 #include <boost/preprocessor/stringize.hpp>
 #include <boost/test/unit_test.hpp>
 #include "json/json_spirit_reader_template.h"
@@ -48,7 +47,7 @@ ParseScript(string s)
     vector<string> words;
     split(words, s, is_any_of(" \t\n"), token_compress_on);
 
-    BOOST_FOREACH(string w, words)
+    for (string w : words)
     {
         if (all(w, is_digit()) ||
             (starts_with(w, "-") && all(string(w.begin()+1, w.end()), is_digit())))
@@ -128,7 +127,7 @@ BOOST_AUTO_TEST_CASE(script_valid)
     // scripts.
     Array tests = read_json("script_valid.json");
 
-    BOOST_FOREACH(Value& tv, tests)
+    for (Value& tv : tests)
     {
         Array test = tv.get_array();
         string strTest = write_string(tv, false);
@@ -152,7 +151,7 @@ BOOST_AUTO_TEST_CASE(script_invalid)
     // Scripts that should evaluate as invalid
     Array tests = read_json("script_invalid.json");
 
-    BOOST_FOREACH(Value& tv, tests)
+    for (Value& tv : tests)
     {
         Array test = tv.get_array();
         string strTest = write_string(tv, false);
@@ -211,7 +210,7 @@ sign_multisig(CScript scriptPubKey, std::vector<CKey> keys, CTransaction transac
     // and vice-versa)
     //
     result << OP_0;
-    BOOST_FOREACH(CKey key, keys)
+    for (CKey key : keys)
     {
         vector<unsigned char> vchSig;
         BOOST_CHECK(key.Sign(hash, vchSig));