Add umedbazarov/ruh-vpn: VPN/proxy manager for sing-box (#304)

* Add umedbazarov/ruh-vpn: VPN/proxy manager for sing-box

New community plugin: bar widget, panel, service and control-center
shortcut for managing SSH, VLESS, VMess, Shadowsocks and SOCKS5
connections through sing-box, with routing presets, custom rules,
system-proxy/TUN modes and a kill switch. The bundled Python backend
serves a loopback control API protected by a per-launch bearer token.

* Address review: sanitize kill-switch ruleset, scope TUN capability, fix mux error path, disclose DNS

- kill switch: only pre-resolved, canonicalized literal IPs enter the nft
  ruleset; domains are resolved first and anything unparseable is dropped,
  so subscription-supplied addresses can no longer inject nft syntax
- TUN: CAP_NET_ADMIN is granted to a plugin-private copy of sing-box in a
  0700 directory instead of the shared system binary; the copy is refreshed
  (clearing the cap) when the system binary changes, and the legacy grant
  on the shared binary is removed in the same polkit prompt
- fix NameError in the mux startup failure path (undefined mux_name) that
  hid the log tail and skipped teardown
- README: disclose plain-UDP DNS endpoints (8.8.8.8 via tunnel, 223.5.5.5
  direct in rules mode) alongside the TUN DoH endpoint

---------

Co-authored-by: Umedjon Bazarov <170195993+UmedjonBA@users.noreply.github.com>

ruh-vpn/shortcut.luau

@@ -0,0 +1,33 @@
+--!nonstrict
+-- shortcut.luau — control-center tile: toggle the proxy on/off.
+
+local nonce = 0
+local function send(method, args)
+  nonce = nonce + 1
+  noctalia.state.set("cmd", { method = method, args = args or {}, nonce = tostring(nonce) .. ":" .. tostring(os.time()) })
+end
+
+local function refresh()
+  local s = noctalia.state.get("status") or {}
+  local running = s.running == true
+  shortcut.setIcon(running and "lock" or "lock-open")
+  shortcut.setLabel(running and noctalia.tr("shortcut.on") or noctalia.tr("shortcut.off"))
+  shortcut.setActive(running)
+end
+
+function update() refresh() end
+
+function onClick()
+  local s = noctalia.state.get("status") or {}
+  if s.running then
+    send("StopProxy", {})
+  else
+    if s.activeServerId and s.activeServerId ~= "" then
+      send("StartProxy", { s.activeServerId, s.mode or "rules", s.proxyMode or "system" })
+    else
+      noctalia.notifyError("VPN", noctalia.tr("error.no-server"))
+    end
+  end
+end
+
+noctalia.setUpdateInterval(2000)