Add report templates and unify template storage

frontend/src/layout/AppShell.tsx

@@ -5,7 +5,8 @@ const PAGE_TITLES: Record<string, string> = {
   "/home": "Startseite",
   "/samples/new": "Neuanlage einer Probe",
   "/portal": "MUH-Portal",
-  "/invoice-template": "Rechnungstemplate",
+  "/invoice-template": "Rechnung",
+  "/report-template": "Bericht",
 };
 
 function resolvePageTitle(pathname: string) {
@@ -80,9 +81,17 @@ export default function AppShell() {
               <div className="nav-group">
                 <div className="nav-group__label">Verwaltung</div>
                 <div className="nav-subnav">
-                  <NavLink to="/invoice-template" className={({ isActive }) => `nav-sublink ${isActive ? "is-active" : ""}`}>
-                    Rechnungstemplate
-                  </NavLink>
+                  <div className="nav-subgroup">
+                    <div className="nav-subgroup__label">Vorlagen</div>
+                    <div className="nav-subnav nav-subnav--nested">
+                      <NavLink to="/invoice-template" className={({ isActive }) => `nav-sublink ${isActive ? "is-active" : ""}`}>
+                        Rechnung
+                      </NavLink>
+                      <NavLink to="/report-template" className={({ isActive }) => `nav-sublink ${isActive ? "is-active" : ""}`}>
+                        Bericht
+                      </NavLink>
+                    </div>
+                  </div>
                   <NavLink to="/admin/landwirte" className={({ isActive }) => `nav-sublink ${isActive ? "is-active" : ""}`}>
                     Landwirte
                   </NavLink>