[Web] Socket listeners & component event handlers never cleaned up

[Flegma]

Summary

Global socket listeners and component-level event handlers are created but never properly removed.

Findings

• Socket.ts — 5 global socket listeners registered at module load. Return values (.stop() methods) never captured.
• ChatLobby.vue — watch on lobbyId assigns new listener without calling .stop() on previous.
• MatchmakingConfirm.vue — countdownInterval may not be cleared if error occurs before unmount.
• StreamGlobal.vue — document event listeners added on mount without duplicate check.

Impact

Accumulated listeners cause duplicate event processing and memory growth.

Suggested Fix

Capture and store all listener return values. Call .stop() on previous before creating new. Clear intervals in error paths.

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Related Issues (Memory Leak Pattern)

• [API] Missing NestJS lifecycle cleanup — intervals, recursive timeouts, stale WS refs #375 — [API] Missing NestJS lifecycle cleanup
• [Web] GraphQL subscription leaks — NotificationStore, ApplicationSettings, Matchmaking, MatchLobby #385 — [Web] GraphQL subscription leaks
• [Web] Socket listeners & component event handlers never cleaned up #386 — [Web] Socket listeners never cleaned up
• [Game Server] Resource disposal — HttpClient, WebSocket, Timer, pending messages accumulation #398 — [Game Server] Resource disposal issues
• [Connector] Network monitoring process leak & throttle instance accumulation #407 — [Connector] Network process leak & throttle accumulation