[Feature Request] Support multiple AmneziaWG instances on different UDP ports per server

[vlnd0]

Summary

Allow installing and managing more than one AmneziaWG instance on the same server, each listening on its own UDP port, from the panel. Currently the panel manages a single AWG installation per server with one fixed port — there is no way to add a second AWG container/interface on another port without doing it manually over SSH (and the panel then doesn't know about it).

Motivation

A single UDP port per server is a single point of failure against ISP-level filtering:

• Some ISPs selectively P ports, and the blockedset differs between ISPs and changes over time (e.g. UDP/443 is commonly
  filtered because of QUICrts still pass).
• When the configured port gets blocked for some users, the whole AWG endpoint
  on that server becomes u recourse today ischanging the port of the single instance — which breaks all previously issued
  client configs at once.
• With multiple instances on diverse ports (e.g. 51820, 4500 /IPsec NAT-T/,
  3478 /STUN/), an operatofigs and migrate themgradually when one port gets blocked — without renting a separate server per
  port.

Proposed behavior

• Install: on a server tdd another AmneziaWGinstance" with a port prompt. Each instance gets its own container/interface and a non-overlapping cl8.2.0/24, …).
• Dashboard: show each instance separately (port, status, peers, traffic),individual start/stop/re
• Users: when creating a user config, let the admin choose which instance (port) it is issued for config per instance forthe same user.
• Detection: the automat detect multiple existingAWG containers/interfaces, not just the first one.
• Firewall: open every is) during install, as isdone for the single instance now.