fix(security): authenticate VNC/terminal WebSockets and harden SSH/config

Critical security and robustness fixes from a code audit:

- WS terminal/VNC now require a JWT (?token=), validate the session,
  vms.console permission and VM ownership before bridging to Proxmox
  (previously the LXC terminal gave unauthenticated root shell access).
  Frontend ConsolePage passes the token in both WS URLs.
- Fix SSH fallback for `pvecm delnode`: SSHClient now supports password
  auth (it previously crashed with TypeError); ProxmoxClient stores the
  password for SSH fallbacks and the host port suffix is stripped.
- Add production startup warnings for default ADMIN_PASSWORD and wildcard
  CORS_ORIGINS.
- dashboard: use tz-aware utcnow() instead of naive datetime.utcnow().
- crypto: narrow decrypt_value except to InvalidToken and log failures.
- ssh_client: guard the shared connection cache with a lock; make
  unknown-host-key rejection opt-in via SSH_REJECT_UNKNOWN_HOSTS.
- logging: send loguru console output to stderr instead of stdout.
- Sync version fallback to 1.5.1; remove one-off refactor scripts.
- Add CODE_REVIEW.md audit report.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/app/api/dashboard.py

@@ -1,11 +1,12 @@
 from fastapi import APIRouter, Depends, Request
 from fastapi.responses import JSONResponse
 from sqlalchemy.orm import Session
-from datetime import datetime, timedelta
+from datetime import timedelta
 
 from ..db import get_db
 from ..models import ProxmoxServer, AuditLog, User
 from ..auth import PermissionChecker
+from ..config import utcnow
 
 router = APIRouter()
 
@@ -39,7 +40,7 @@ def dashboard_stats(
         cluster_q = cluster_q.filter(ProxmoxServer.id.in_(server_ids))
     total_clusters = cluster_q.scalar() or 0
 
-    since_24h = datetime.utcnow() - timedelta(hours=24)
+    since_24h = utcnow() - timedelta(hours=24)
     total_alerts = db.query(AuditLog).filter(
         AuditLog.level.in_(['error', 'critical']),
         AuditLog.created_at >= since_24h
@@ -88,7 +89,7 @@ def get_dashboard_alerts(
     current_user: User = Depends(PermissionChecker("logs.view"))
 ):
     """Вернуть события error/critical за последние 24 ч для дашборда"""
-    since_24h = datetime.utcnow() - timedelta(hours=24)
+    since_24h = utcnow() - timedelta(hours=24)
     alerts = db.query(AuditLog).filter(
         AuditLog.level.in_(['error', 'critical']),
         AuditLog.created_at >= since_24h