Migrate inventory and reports to the SPA

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/components/Header.tsx

@@ -32,6 +32,16 @@ export const Header = (): JSX.Element => {
               Logg
             </NavLink>
           </li>
+          <li>
+            <NavLink to="/inventory" className={navLinkStyles}>
+              Varebeholdning
+            </NavLink>
+          </li>
+          <li>
+            <NavLink to="/report" className={navLinkStyles}>
+              Rapport
+            </NavLink>
+          </li>
           <li>
             <NavLink to="/stats" className={navLinkStyles}>
               Statistikk