Cleanup: drop boost::filesystem/thread/chrono, retire dead code

Migration from boost to std-library equivalents and removal of unreachable
code paths. Touches infrastructure only — no consensus rule or wallet
serialization changes.

Dead code removed:
- IRC bootstrap (irc.cpp/h, 417 lines): orphan from pre-Tor era, no callers.
- Alert system (alert.cpp/h + sendalert RPC + Qt UI signal, ~500 lines):
  retired post-V5 fork; old peers' alert messages now hit the unknown-cmd
  default branch, logged + ignored.
- Legacy P2P handlers in main.cpp: "checkpoint" (already a no-op stub since
  V5 fork master-key removal), "checkorder"/"reply" (2010-era Receive-by-IP
  feature), plus their unused supporting structures (CRequestTracker,
  PushRequest overloads, mapRequests/cs_mapRequests, mapReuseKey).
- Unreachable RPCs clearwallettransactions and scanforalltxns (~175 lines):
  defined in rpcwallet.cpp but never registered in the dispatch table.
- Stale -alertnotify CLI help text (option was advertised but never wired).

boost::filesystem -> std::filesystem (C++17):
- 30 source files, 5 headers. namespace fs = boost::filesystem swapped to
  namespace fs = std::filesystem; boost::filesystem::ifstream/ofstream
  replaced with std::ifstream/ofstream (path-aware in C++17);
  fs::system_complete -> fs::absolute; boost::filesystem::filesystem_error
  -> std::filesystem::filesystem_error.
- Build system: dropped Boost::filesystem from link libs and Boost
  components; PCH includes updated.
- Added explicit <filesystem> includes where types were previously
  available only transitively (db.h, rpcblockchain.cpp).

boost::thread -> std::thread (12 files):
- sync.h CCriticalSection/CWaitableCriticalSection now alias
  std::recursive_mutex/std::mutex. boost::unique_lock and
  boost::condition_variable / boost::mutex::scoped_lock swapped to std
  equivalents; sync.cpp boost::thread_specific_ptr -> thread_local
  std::unique_ptr.
- init.cpp boost::thread_group rewritten as std::vector<std::thread> with
  manual join loop. boost::thread::hardware_concurrency ->
  std::thread::hardware_concurrency.
- main.cpp/wallet.cpp -blocknotify/-walletnotify shell-out threads now use
  std::thread(...).detach() — fixes a latent bug where modern boost::thread
  destructor would call std::terminate on the joinable thread.
- util.cpp NewThread now catches std::system_error.
- No interruption_point/interrupt usage anywhere — pure mechanical swap.

boost::chrono / boost::posix_time -> std::chrono (3 of 5 files):
- util.h: MilliSleep, GetTimeMillis, GetTimeMicros rewritten on std::chrono
  (system_clock for epoch math, sleep_for for delays).
- snapshotnet.cpp: sleep_for swapped.
- DoS_tests.cpp: timing harness uses steady_clock.
- Skipped: rpcdump.cpp (boost::posix_time::time_input_facet has no clean
  std::get_time equivalent) and qt/qtipcserver.cpp (locked to
  boost::posix_time by boost::interprocess::message_queue::timed_receive).

Other housekeeping:
- Dropped unnecessary "using namespace boost;" from txdb-leveldb.cpp,
  txdb-rocksdb.cpp, walletdb.cpp, db.cpp (verified no unqualified boost
  names in those TUs).
- Removed unused extern declaration for clearwallettransactions.

Build fixes for non-unity builds on MinGW64/GCC 15:
- net.cpp: dropped stale #include "irc.h".
- addrman.cpp + main.cpp: explicit <cmath> include for sqrt/pow (was
  arriving transitively via boost headers).
- rpcblockchain.cpp + init.cpp: defensive #undef STRICT/ADVISORY/PERMISSIVE
  since windows.h macros collide with the Checkpoints:: enum values when
  std headers reorder include flow.
- tor_embed_hooks.cpp: triangles_tor_check_interrupted now polls fShutdown
  instead of boost::this_thread::interruption_requested (we never used
  boost interruption — the hook was always effectively a no-op).
- snapshotnet.cpp: fs::remove error handle uses std::error_code.
- serialize.h: added <ios> for std::ios::badbit/failbit (was relying on
  transitive include via boost).

Note: unity builds currently fail on this branch due to std::byte (C++17)
colliding with COM 'byte' typedef from shlobj.h when 'using namespace std;'
from earlier files in the unity slice leaks into util.cpp's parse of
shlobj.h. Build with -DENABLE_UNITY_BUILD=OFF (the default).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/qt/guiutil.cpp

@@ -20,8 +20,8 @@
 #include <QDesktopServices>
 #include <QThread>
 
-#include <boost/filesystem.hpp>
-#include <boost/filesystem/fstream.hpp>
+#include <filesystem>
+#include <fstream>
 
 #ifdef WIN32
 #ifdef _WIN32_WINNT
@@ -240,10 +240,10 @@ bool isObscured(QWidget *w)
 
 void openDebugLogfile()
 {
-    boost::filesystem::path pathDebug = GetDataDir() / "debug.log";
+    std::filesystem::path pathDebug = GetDataDir() / "debug.log";
 
     /* Open debug.log with the associated application */
-    if (boost::filesystem::exists(pathDebug))
+    if (std::filesystem::exists(pathDebug))
         QDesktopServices::openUrl(QUrl::fromLocalFile(QString::fromStdString(pathDebug.string())));
 }
 
@@ -272,7 +272,7 @@ bool ToolTipToRichTextFilter::eventFilter(QObject *obj, QEvent *evt)
 }
 
 #ifdef WIN32
-boost::filesystem::path static StartupShortcutPath()
+std::filesystem::path static StartupShortcutPath()
 {
     return GetSpecialFolderPath(CSIDL_STARTUP) / "triangles.lnk";
 }
@@ -280,13 +280,13 @@ boost::filesystem::path static StartupShortcutPath()
 bool GetStartOnSystemStartup()
 {
     // check for triangles.lnk
-    return boost::filesystem::exists(StartupShortcutPath());
+    return std::filesystem::exists(StartupShortcutPath());
 }
 
 bool SetStartOnSystemStartup(bool fAutoStart)
 {
     // If the shortcut exists already, remove it for updating
-    boost::filesystem::remove(StartupShortcutPath());
+    std::filesystem::remove(StartupShortcutPath());
 
     if (fAutoStart)
     {
@@ -343,9 +343,9 @@ bool SetStartOnSystemStartup(bool fAutoStart)
 // Follow the Desktop Application Autostart Spec:
 //  http://standards.freedesktop.org/autostart-spec/autostart-spec-latest.html
 
-boost::filesystem::path static GetAutostartDir()
+std::filesystem::path static GetAutostartDir()
 {
-    namespace fs = boost::filesystem;
+    namespace fs = std::filesystem;
 
     char* pszConfigHome = getenv("XDG_CONFIG_HOME");
     if (pszConfigHome) return fs::path(pszConfigHome) / "autostart";
@@ -354,14 +354,14 @@ boost::filesystem::path static GetAutostartDir()
     return fs::path();
 }
 
-boost::filesystem::path static GetAutostartFilePath()
+std::filesystem::path static GetAutostartFilePath()
 {
     return GetAutostartDir() / "triangles.desktop";
 }
 
 bool GetStartOnSystemStartup()
 {
-    boost::filesystem::ifstream optionFile(GetAutostartFilePath());
+    std::ifstream optionFile(GetAutostartFilePath());
     if (!optionFile.good())
         return false;
     // Scan through file for "Hidden=true":
@@ -381,7 +381,7 @@ bool GetStartOnSystemStartup()
 bool SetStartOnSystemStartup(bool fAutoStart)
 {
     if (!fAutoStart)
-        boost::filesystem::remove(GetAutostartFilePath());
+        std::filesystem::remove(GetAutostartFilePath());
     else
     {
         char pszExePath[MAX_PATH+1];
@@ -389,9 +389,9 @@ bool SetStartOnSystemStartup(bool fAutoStart)
         if (readlink("/proc/self/exe", pszExePath, sizeof(pszExePath)-1) == -1)
             return false;
 
-        boost::filesystem::create_directories(GetAutostartDir());
+        std::filesystem::create_directories(GetAutostartDir());
 
-        boost::filesystem::ofstream optionFile(GetAutostartFilePath(), std::ios_base::out|std::ios_base::trunc);
+        std::ofstream optionFile(GetAutostartFilePath(), std::ios_base::out|std::ios_base::trunc);
         if (!optionFile.good())
             return false;
         // Write a triangles.desktop file to the autostart directory:
@@ -407,15 +407,15 @@ bool SetStartOnSystemStartup(bool fAutoStart)
 }
 #elif defined(Q_OS_MAC) || defined(MAC_OSX) || defined(__APPLE__)
 
-boost::filesystem::path static GetLaunchAgentsDir()
+std::filesystem::path static GetLaunchAgentsDir()
 {
     const QString homeDir = QStandardPaths::writableLocation(QStandardPaths::HomeLocation);
     if (homeDir.isEmpty())
-        return boost::filesystem::path();
-    return boost::filesystem::path(homeDir.toStdString()) / "Library" / "LaunchAgents";
+        return std::filesystem::path();
+    return std::filesystem::path(homeDir.toStdString()) / "Library" / "LaunchAgents";
 }
 
-boost::filesystem::path static GetAutostartFilePath()
+std::filesystem::path static GetAutostartFilePath()
 {
     return GetLaunchAgentsDir() / "org.triangles.triangles-qt.plist";
 }
@@ -441,7 +441,7 @@ static std::string PlistEscape(const std::string& value)
 
 bool GetStartOnSystemStartup()
 {
-    boost::filesystem::ifstream optionFile(GetAutostartFilePath());
+    std::ifstream optionFile(GetAutostartFilePath());
     if (!optionFile.good())
         return false;
 
@@ -459,16 +459,16 @@ bool GetStartOnSystemStartup()
 bool SetStartOnSystemStartup(bool fAutoStart)
 {
     if (!fAutoStart)
-        return !boost::filesystem::exists(GetAutostartFilePath()) || boost::filesystem::remove(GetAutostartFilePath());
+        return !std::filesystem::exists(GetAutostartFilePath()) || std::filesystem::remove(GetAutostartFilePath());
 
     const QString exePath = QApplication::applicationFilePath();
     if (exePath.isEmpty())
         return false;
 
     const QString workingDir = QFileInfo(exePath).absolutePath();
-    boost::filesystem::create_directories(GetLaunchAgentsDir());
+    std::filesystem::create_directories(GetLaunchAgentsDir());
 
-    boost::filesystem::ofstream optionFile(GetAutostartFilePath(), std::ios_base::out|std::ios_base::trunc);
+    std::ofstream optionFile(GetAutostartFilePath(), std::ios_base::out|std::ios_base::trunc);
     if (!optionFile.good())
         return false;