Panel redesign, per-server I1 masking, node minimum version 0.5.0, installer output

- UI: settings tab with sections (server, API keys, Prometheus, audit, migrate,
  about); server settings moved there; master keys table rework (menu, chips,
  version, compact phone cards); three-state node version chip
- I1: random per-server template (DNS / QUIC Initial / STUN) kept in users.db,
  GET/POST /api/masking, change from the master keys banner
- Hub rejects nodes older than 0.5.0 (close 4026), /ui/nodes reports outdated
- install.sh: spinner for long commands (full output in the log), step progress
  bar, cards; installs older than 0.5.0 require a full reinstall with data reset
- Bump to Beta 0.5.0

awg-ui/src/lib/theme.ts

@@ -0,0 +1,47 @@
+// Copyright (c) 2026 Ivan Vasilev
+// This source code is licensed under the MIT license found in the
+// LICENSE file in the root directory of this source tree.
+// Тема панели: светлая, тёмная или как в системе. Одно хранилище на всё приложение —
+// переключатель в шапке и вкладка «Настройки» читают и меняют его через useTheme().
+import { useSyncExternalStore } from 'react';
+import { THEME_KEY } from './shared';
+
+export type ThemeMode = 'light' | 'dark' | 'system';
+export type Theme = 'light' | 'dark';
+
+const dark = window.matchMedia('(prefers-color-scheme: dark)');
+const listeners = new Set<() => void>();
+
+function readMode(): ThemeMode {
+    try {
+        const v = localStorage.getItem(THEME_KEY);
+        if (v === 'dark' || v === 'system') return v;
+    } catch { /* не критично */ }
+    return 'light';   // без сохранённого выбора — светлая, как было до режима «как в системе»
+}
+
+let mode = readMode();
+const resolved = (): Theme => (mode === 'system' ? (dark.matches ? 'dark' : 'light') : mode);
+
+function apply() {
+    document.documentElement.setAttribute('data-theme', resolved());
+    listeners.forEach(l => l());
+}
+// «Как в системе» следует за сменой темы ОС на лету
+dark.addEventListener('change', () => { if (mode === 'system') apply(); });
+apply();
+
+export function setThemeMode(next: ThemeMode) {
+    mode = next;
+    try { localStorage.setItem(THEME_KEY, next); } catch { /* не критично */ }
+    apply();
+}
+
+const subscribe = (l: () => void) => { listeners.add(l); return () => { listeners.delete(l); }; };
+
+// mode — выбор пользователя, theme — что реально применено.
+export function useTheme(): { mode: ThemeMode; theme: Theme } {
+    const snap = useSyncExternalStore(subscribe, () => `${mode}:${resolved()}`);
+    const [m, t] = snap.split(':') as [ThemeMode, Theme];
+    return { mode: m, theme: t };
+}