feat: Move version number to sidebar next to MUH logo

- Add version number in small font next to MUH logo in sidebar
- Remove version footer from HomePage
- Add CSS styling for sidebar version display

frontend/src/layout/AppShell.tsx

@@ -1,5 +1,6 @@
 import { NavLink, Outlet, useLocation, useNavigate } from "react-router-dom";
 import { useSession } from "../lib/session";
+import { APP_VERSION } from "../lib/version";
 
 const PAGE_TITLES: Record<string, string> = {
   "/home": "Startseite",
@@ -39,7 +40,9 @@ export default function AppShell() {
     <div className="app-shell">
       <aside className="sidebar">
         <div className="sidebar__brand">
-          <div className="sidebar__logo">MUH</div>
+          <div className="sidebar__logo">
+            MUH <span className="sidebar__version">({APP_VERSION})</span>
+          </div>
         </div>
 
         <nav className="sidebar__nav">