feat: implement dynamic sidebar with server-side menu translation

- Add server-side translation for menu labels using user's preferred_language
- Replace hardcoded sidebar template with dynamic rendering from menu API
- Remove hardcoded section/page mappings in favor of menu discovery
- Fix locale file structure (move menu keys to top level to avoid double-nesting)
- Sidebar now fully driven by /admin/menu-config/render/admin API endpoint

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/modules/payments/locales/de.json

@@ -1,12 +1,12 @@
 {
+  "menu": {
+    "payments": "Zahlungen"
+  },
   "payments": {
-    "title": "Zahlungen",
-    "menu": {
-      "payments": "Zahlungen"
-    },
-    "messages": {
-      "payment_successful": "Zahlung erfolgreich verarbeitet",
-      "payment_failed": "Zahlungsverarbeitung fehlgeschlagen"
-    }
+    "title": "Zahlungen"
+  },
+  "messages": {
+    "payment_successful": "Zahlung erfolgreich verarbeitet",
+    "payment_failed": "Zahlungsverarbeitung fehlgeschlagen"
   }
 }

app/modules/payments/locales/en.json

@@ -1,12 +1,12 @@
 {
+  "menu": {
+    "payments": "Payments"
+  },
   "payments": {
-    "title": "Payments",
-    "menu": {
-      "payments": "Payments"
-    },
-    "messages": {
-      "payment_successful": "Payment processed successfully",
-      "payment_failed": "Payment processing failed"
-    }
+    "title": "Payments"
+  },
+  "messages": {
+    "payment_successful": "Payment processed successfully",
+    "payment_failed": "Payment processing failed"
   }
 }

app/modules/payments/locales/fr.json

@@ -1,12 +1,12 @@
 {
+  "menu": {
+    "payments": "Paiements"
+  },
   "payments": {
-    "title": "Paiements",
-    "menu": {
-      "payments": "Paiements"
-    },
-    "messages": {
-      "payment_successful": "Paiement traité avec succès",
-      "payment_failed": "Échec du traitement du paiement"
-    }
+    "title": "Paiements"
+  },
+  "messages": {
+    "payment_successful": "Paiement traité avec succès",
+    "payment_failed": "Échec du traitement du paiement"
   }
 }

app/modules/payments/locales/lb.json

@@ -1,12 +1,12 @@
 {
+  "menu": {
+    "payments": "Bezuelungen"
+  },
   "payments": {
-    "title": "Bezuelungen",
-    "menu": {
-      "payments": "Bezuelungen"
-    },
-    "messages": {
-      "payment_successful": "Bezuelung erfollegräich veraarbecht",
-      "payment_failed": "Bezuelungsveraarbechtung ass feelgeschloen"
-    }
+    "title": "Bezuelungen"
+  },
+  "messages": {
+    "payment_successful": "Bezuelung erfollegräich veraarbecht",
+    "payment_failed": "Bezuelungsveraarbechtung ass feelgeschloen"
   }
 }