p2p: Bound goodbye context with timeout to prevent blocking disconnections

[maradini77]

Description

• Summary: Replace context.TODO() with a bounded context when sending the goodbye message during peer disconnection.
• Motivation: Unbounded calls can hang under network issues, degrading shutdown responsiveness and operational stability.
• Change: Use context.WithTimeout(context.Background(), 5s) for goodByeFunc in disconnect path; add a brief comment.
• Impact: More deterministic disconnect behavior; no protocol or API changes.