Backend, Transport Module Refactor

[vasyl-ks]

Summary

Refactor transport to improve reliability, test coverage and performance by reducing per-packet allocations.

Implementation

• Pooling: enable packet pooling; add pooled packets, encoder buffers, and UDP bytes.Reader reuse to cut allocations.
• Concurrency: switch connection locking to RWMutex; use read locks on send paths.
• Handlers: refactor TCP handling into smaller helpers; rename TCP connection helpers; add a UDP fault-replication helper.
• Logging & errors: reuse loggers in hot paths; stop using the testing logger in transport; guard errChan sends to avoid nil error notifications.
• Startup: add logger start hook and notify the frontend on start.
• Tests: add/extend integration tests for handleConversation and handleSniffer; add unit coverage for packet handling, errors/notifications, TFTP read/write, and TCP/UDP server handlers; stabilize UDP tests by releasing pooled buffers and wiring encoder for packet id 100.