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/proxmox/client.py

@@ -101,6 +101,8 @@ class ProxmoxClient(VmMixin, LxcMixin, ClusterMixin, StorageMixin, NetworkMixin,
             self.host = host
             self.user = user
             self.timeout = timeout
+            # Stored for SSH fallbacks (e.g. pvecm delnode) that need root password auth
+            self._password = password
             # Улучшенный ключ кеша - включаем token_name для уникальности
             self.connection_key = f"{host}:{user}:{token_name or 'password'}"
             self.proxmox = None