Show BanGUI app version in sidebar, fix version tooltips

- Inject __APP_VERSION__ at build time via vite.config.ts define (reads
  frontend/package.json#version); declare the global in vite-env.d.ts.
- Render 'BanGUI v{__APP_VERSION__}' in the sidebar footer (MainLayout)
  when expanded; hidden when collapsed.
- Rename fail2ban version tooltip to 'fail2ban daemon version' in
  ServerStatusBar so it is visually distinct from the app version.
- Sync frontend/package.json version (0.9.0 → 0.9.3) to match
  Docker/VERSION; update release.sh to keep them in sync on every bump.
- Add vitest define stub for __APP_VERSION__ so tests compile cleanly.
- Add ServerStatusBar and MainLayout test suites (10 new test cases).

frontend/vite.config.ts

@@ -1,10 +1,19 @@
 import { defineConfig } from "vite";
 import react from "@vitejs/plugin-react";
 import { resolve } from "path";
+import { readFileSync } from "node:fs";
+
+const pkg = JSON.parse(
+  readFileSync(resolve(__dirname, "package.json"), "utf-8"),
+) as { version: string };
 
 // https://vitejs.dev/config/
 export default defineConfig({
   plugins: [react()],
+  define: {
+    /** BanGUI application version injected at build time from package.json. */
+    __APP_VERSION__: JSON.stringify(pkg.version),
+  },
   resolve: {
     alias: {
       "@": resolve(__dirname, "src"),