refactor(zenoh): Thread safety audit of all locking patterns

[zhexuany]

Refactoring Task

Conduct a full audit of all locking patterns in the C++ Zenoh plugin.

Motivation

Thread safety is critical for the Zenoh plugin which handles concurrent subscribe/publish operations. A comprehensive audit ensures:

• No deadlocks from lock ordering issues
• No race conditions from unlocked access
• Proper RAII lock guard usage

Scope

Review all files in middlewares/zenoh/src/zenoh_plugin/src/:

1. Check all mutex lock/unlock patterns
2. Verify lock ordering to prevent deadlocks
3. Ensure atomic operations are used correctly
4. Review std::lock_guard vs std::unique_lock usage

Priority

High - Thread safety bugs can cause data corruption and crashes