chore: unify version to 9.7.0 with single source of truth

- Add VERSION file at project root as canonical version source
- Sync all version references: package.json, pyproject.toml, config.py,
  Chart.yaml, docs/CONFIGURATION.md (all were out of sync: 9.0.1, v9.6, 0.1.0)
- Replace hardcoded v9.6 in SettingsPage and About page with dynamic
  APP_VERSION import from @/lib/version.ts
- Add Vite define for __APP_VERSION__ reading from package.json at build time
- Add TypeScript global declaration for __APP_VERSION__

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/routes/_authenticated/about.tsx

@@ -1,6 +1,7 @@
 import { createFileRoute } from '@tanstack/react-router'
 import { useEffect, useRef, useState } from 'react'
 import { RugLogo } from '@/components/brand/RugLogo'
+import { APP_VERSION } from '@/lib/version'
 
 export const Route = createFileRoute('/_authenticated/about')({
   component: AboutPage,
@@ -509,7 +510,7 @@ function AboutPage() {
           MSP fleet management platform for RouterOS devices
         </p>
         <span className="inline-block px-3 py-1 text-xs font-mono font-medium text-accent bg-accent-muted rounded-full">
-          v9.6
+          {APP_VERSION}
         </span>
       </div>