feat(logger): update logger configuration to set log level to Fatal to eliminate IO lock contention

fix(redis): silence Redis internal logging and optimize connection pool settings to reduce mutex contention

feat(userlist): enhance user list component with avatar support and improved styling

test(load): add production-style load test script for WebSocket connections and Redis PubSub stress testing

chore(loadtest): create script to run load tests with pprof profiling for performance analysis

backend/.env.example

@@ -62,3 +62,14 @@ GITHUB_CLIENT_SECRET=your-github-client-secret
 
 # Redis (for future use)
 REDIS_URL=redis://localhost:6379
+
+# ===================
+# PROFILING (pprof)
+# ===================
+# Enable pprof endpoints at /debug/pprof/* (non-production only)
+# ENABLE_PPROF=1
+# Only allow requests from localhost/loopback (recommended)
+# PPROF_LOCAL_ONLY=true
+# Optional: contention profiling (adds overhead; best for short windows)
+# PPROF_BLOCK_RATE=1
+# PPROF_MUTEX_FRACTION=1