refactor(sonar): assorted small fixes

- empty() instead of size() comparisons (cpp:S1155)
- member initialisers in declaration order (cpp:S3229)
- no redundant c_str() when a std::string is accepted (cpp:S7121)
- contains() on associative containers (cpp:S6171)
- const reference instead of a copying range-for (cpp:S6032)
- starts_with() for prefix checks (cpp:S6178)
- no std::move on temporaries (cpp:S5274)
- has_value() on std::optional (cpp:S7172)
- bool literals for bool members (cpp:S5820)
- inline only on the definition (cpp:S3548)
- explicit base access specifier (cpp:S5965)
- explicit element access instead of dereferencing an array (cpp:S7116)
- rely on the C++20 rewritten operator!= (cpp:S6186)

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

network/backend/asio.cpp

@@ -111,7 +111,7 @@ void network::tcp::connection::write_message(const message &msg, std::ostream &s
 
 void network::tcp::connection::send_messages(const std::vector<std::shared_ptr<message> > &messages)
 {
-	if (messages.size() == 0)
+	if (messages.empty())
 		return;
 
 	std::ostringstream stream;
@@ -173,7 +173,7 @@ void network::tcp::server::handle_accept(std::shared_ptr<connection> conn, const
 // ------------------
 
 network::tcp::client::client(asio::io_context &io_ctxx, const std::string &hostarg, uint32_t portarg)
-    : host(hostarg), port(portarg), io_ctx(io_ctxx)
+    : io_ctx(io_ctxx), host(hostarg), port(portarg)
 {
 }