fix(i18n): complete translations for production launch and fix CMS store context

- Replace CMS custom get_store_context() with core utility (same fix as loyalty)
- Add 85 missing translation keys across fr/de/lb for core, tenancy, messaging,
  customers, and loyalty modules
- Convert 21 client-side $t() calls to server-side _() in 9 loyalty templates
- Fix 3 broken translation keys in store/cards.html

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

static/locales/de.json

@@ -220,6 +220,10 @@
     "datetime": "DD.MM.YYYY HH:mm",
     "currency": "{amount} {symbol}"
   },
+  "clipboard": {
+    "copied": "In die Zwischenablage kopiert",
+    "failed": "Kopieren fehlgeschlagen"
+  },
   "onboarding": {
     "banner": {
       "title": "Erste Schritte",

static/locales/fr.json

@@ -220,6 +220,10 @@
     "datetime": "DD/MM/YYYY HH:mm",
     "currency": "{amount} {symbol}"
   },
+  "clipboard": {
+    "copied": "Copié dans le presse-papiers",
+    "failed": "Échec de la copie"
+  },
   "onboarding": {
     "banner": {
       "title": "Premiers pas",

static/locales/lb.json

@@ -220,6 +220,10 @@
     "datetime": "DD.MM.YYYY HH:mm",
     "currency": "{amount} {symbol}"
   },
+  "clipboard": {
+    "copied": "An d'Zwëschenoflag kopéiert",
+    "failed": "Kopéiere feelgeschloen"
+  },
   "onboarding": {
     "banner": {
       "title": "Ufänken",