wallet_rpc_server: add HTTP body size limit

Set m_max_content_length to MAX_RPC_CONTENT_LENGTH (1MB) to match
the protection already implemented in core_rpc_server. This prevents
memory exhaustion attacks via unlimited HTTP request sizes.

src/wallet/wallet_rpc_server.cpp

@@ -398,6 +398,7 @@ namespace tools
     }
 
     m_net_server.set_threads_prefix("RPC");
+    m_net_server.get_config_object().m_max_content_length = MAX_RPC_CONTENT_LENGTH * 100;
     auto rng = [](size_t len, uint8_t *ptr) { return crypto::rand(len, ptr); };
     return epee::http_server_impl_base<wallet_rpc_server, connection_context>::init(
       rng, std::move(bind_port), std::move(rpc_config->bind_ip),