feat(cdclient): make a new CDServer.sqlite off-thread and swap tables in place

CDClientSnapshot converts a copy of the client's fdb into its own
CDServer-<hash>.sqlite with the cdserver migrations applied, on its own
connection. CDClientDatabase::Reconnect opens the new file before letting go
of the old one; CDClientManager::Reload empties every table (old entries kept
alive so references from spawned objects stay valid), retires the old fdb view
and loads again.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dDatabase/CDClientDatabase/CDClientDatabase.cpp

@@ -67,6 +67,23 @@ void CDClientDatabase::Connect(const std::string& filename) {
 	sqlite3_trace_v2(conn->handle(), SQLITE_TRACE_STMT | SQLITE_TRACE_PROFILE, Trace, nullptr);
 }
 
+void CDClientDatabase::Reconnect(const std::string& filename) {
+	auto* next = new CppSQLite3DB();
+	try {
+		next->open(filename.c_str());
+	} catch (...) {
+		delete next;
+		throw;
+	}
+	sqlite3_trace_v2(next->handle(), SQLITE_TRACE_STMT | SQLITE_TRACE_PROFILE, Trace, nullptr);
+	g_Running.clear();
+	auto* old = std::exchange(conn, next);
+	isConnected = true;
+	// close_v2 waits for statements still open on the old file (a query a caller holds) before it really closes. The
+	// wrapper is left behind on purpose: its destructor would close the handle a second time
+	sqlite3_close_v2(old->handle());
+}
+
 //! Queries the CDClient
 CppSQLite3Query CDClientDatabase::ExecuteQuery(const std::string& query) {
 	return conn->execQuery(query.c_str());