fix(json): use local CharReaderBuilder for thread safety

[xander1421]

Problem

Crash with:

unhandled exception (type std::exception) in signal handler:
what: in Json::Value::find(begin, end): requires objectValue or nullValue

Root Cause

The JsonParser class uses a shared CharReaderBuilder member that gets accessed concurrently from multiple threads:

• IPC thread: Event handlers call getSocket1JsonReply() → parser_.parse()
• GTK thread: Update functions call getSocket1JsonReply() → parser_.parse()

Each module has its own mutex, but they all share the same IPC::inst() singleton. The module mutexes don't protect the shared parser.

Json::CharReaderBuilder is not thread-safe for concurrent use without synchronization.

Fix

Use a local CharReaderBuilder in parse() instead of a member variable. This makes each parse call independent and thread-safe.

[Alexays]

Thanks!