Harden malformed vehicle packet parsing (#475)

## Summary
Reject malformed vehicle reset and paint packets before slicing
structured payloads, and catch parser exceptions in the TCP client loop.

## Problem
Or:<pid>-<vid>:null and similarly malformed Op packets could reach
substr(npos) in ParseVehicle, throwing std::out_of_range. On TCP, that
exception could escape the client loop and kill the thread.

## Changes
- Guard Or reset packets when no { payload exists
- Guard Op paint packets when no [ payload exists
- Add a small helper and unit test for structured payload extraction
- Catch std::exception around GlobalParser in the TCP client loop and
disconnect the offending client

## Verification
- git diff --check
- Full build/tests not run in this shell because cmake was not installed

src/TNetwork.cpp

@@ -670,7 +670,13 @@ void TNetwork::TCPClient(const std::weak_ptr<TClient>& c) {
             Client->Disconnect("TCPRcv failed");
             break;
         }
+        try {
             mServer.GlobalParser(c, std::move(res), mPPSMonitor, *this, false);
+        } catch (const std::exception& e) {
+            beammp_warnf("Failed to receive/parse packet via TCP from client {}: {}", Client->GetID(), e.what());
+            Client->Disconnect("Failed to parse packet");
+            break;
+        }
     }
 
     if (QueueSync.joinable())

src/TServer.cpp

@@ -28,6 +28,7 @@
 #include <any>
 #include <optional>
 #include <sstream>
+#include <utility>
 
 #include <nlohmann/json.hpp>
 
@@ -53,7 +54,6 @@ static std::optional<std::pair<int, int>> GetPidVid(const std::string& str) {
     }
     return std::nullopt;
 }
-
 TEST_CASE("GetPidVid") {
     SUBCASE("Valid singledigit") {
         const auto MaybePidVid = GetPidVid("0-1");
@@ -120,7 +120,6 @@ TEST_CASE("GetPidVid") {
         CHECK(!MaybePidVid);
     }
 }
-
 TServer::TServer(const std::vector<std::string_view>& Arguments) {
     beammp_info("BeamMP Server v" + Application::ServerVersionString());
     Application::SetSubsystemStatus("Server", Application::Status::Starting);
@@ -472,7 +471,13 @@ void TServer::ParseVehicle(TClient& c, const std::string& Pckt, TNetwork& Networ
         }
 
         if (PID != -1 && VID != -1 && PID == c.GetID()) {
-            Data = Data.substr(Data.find('{'));
+            auto BracketPos = Data.find('{');
+            if (BracketPos == std::string::npos) {
+                beammp_debugf("Invalid 'Or' packet body from client {}", c.GetID());
+                return;
+            }
+
+            Data = Data.substr(BracketPos);
             LuaAPI::MP::Engine->ReportErrors(LuaAPI::MP::Engine->TriggerEvent("onVehicleReset", "", c.GetID(), VID, Data));
             Network.SendToAll(&c, StringToVector(Packet), false, true);
         }
@@ -501,7 +506,14 @@ void TServer::ParseVehicle(TClient& c, const std::string& Pckt, TNetwork& Networ
         }
 
         if (PID != -1 && VID != -1 && PID == c.GetID()) {
-            Data = Data.substr(Data.find('['));
+            auto BracketPos = Data.find('[');
+            if (BracketPos == std::string::npos) {
+                beammp_debugf("Invalid 'Op' packet body from client {}", c.GetID());
+                return;
+            }
+
+            Data = Data.substr(BracketPos);
+
             LuaAPI::MP::Engine->ReportErrors(LuaAPI::MP::Engine->TriggerEvent("onVehiclePaintChanged", "", c.GetID(), VID, Data));
             Network.SendToAll(&c, StringToVector(Packet), false, true);