fix(i18n): add missing menu translations and fix admin language resolution

Two issues caused the admin sidebar to show a mix of French and English:

1. Only 3 of 14 modules had "menu" translations in their locale files.
   When a key was missing, _translate_label() fell back to English Title
   Case from the key name — mixing with French from modules that had
   translations. Added menu sections to all 4 languages (en, fr, de, lb)
   across 13 modules.

2. The language middleware hardcoded admin to "en" ignoring user preference,
   while the menu API fell back to DEFAULT_LANGUAGE ("fr") when
   preferred_language was NULL. Fixed middleware to respect user's
   preferred_language and menu API to use middleware-resolved language
   as fallback.

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

app/modules/loyalty/locales/en.json

@@ -1,72 +1,81 @@
 {
-  "loyalty": {
-    "module": {
-      "name": "Loyalty Programs",
-      "description": "Stamp-based and points-based loyalty programs with wallet integration"
+    "loyalty": {
+        "module": {
+            "name": "Loyalty Programs",
+            "description": "Stamp-based and points-based loyalty programs with wallet integration"
+        },
+        "program": {
+            "title": "Loyalty Program",
+            "create": "Create Program",
+            "edit": "Edit Program",
+            "activate": "Activate",
+            "deactivate": "Deactivate",
+            "type": {
+                "stamps": "Stamps",
+                "points": "Points",
+                "hybrid": "Hybrid"
+            }
+        },
+        "card": {
+            "title": "Loyalty Card",
+            "number": "Card Number",
+            "qr_code": "QR Code",
+            "enroll": "Enroll Customer",
+            "deactivate": "Deactivate Card"
+        },
+        "stamp": {
+            "title": "Stamps",
+            "add": "Add Stamp",
+            "redeem": "Redeem Reward",
+            "count": "{current} of {target}",
+            "until_reward": "{count} until reward"
+        },
+        "points": {
+            "title": "Points",
+            "earn": "Earn Points",
+            "redeem": "Redeem Points",
+            "balance": "{count} points",
+            "per_euro": "{points} points per euro"
+        },
+        "pin": {
+            "title": "Staff PINs",
+            "create": "Create PIN",
+            "edit": "Edit PIN",
+            "unlock": "Unlock PIN",
+            "locked": "PIN locked until {time}"
+        },
+        "wallet": {
+            "google": "Add to Google Wallet",
+            "apple": "Add to Apple Wallet"
+        },
+        "stats": {
+            "title": "Statistics",
+            "total_cards": "Total Cards",
+            "active_cards": "Active Cards",
+            "stamps_issued": "Stamps Issued",
+            "rewards_redeemed": "Rewards Redeemed"
+        },
+        "errors": {
+            "program_not_found": "Loyalty program not found",
+            "program_inactive": "Loyalty program is not active",
+            "card_not_found": "Loyalty card not found",
+            "card_inactive": "Loyalty card is not active",
+            "cooldown": "Please wait {minutes} minutes before next stamp",
+            "daily_limit": "Daily stamp limit of {limit} reached",
+            "insufficient_stamps": "Need {required} stamps, have {current}",
+            "insufficient_points": "Need {required} points, have {current}",
+            "pin_required": "Staff PIN is required",
+            "pin_invalid": "Invalid staff PIN",
+            "pin_locked": "PIN locked due to too many failed attempts"
+        }
     },
-    "program": {
-      "title": "Loyalty Program",
-      "create": "Create Program",
-      "edit": "Edit Program",
-      "activate": "Activate",
-      "deactivate": "Deactivate",
-      "type": {
-        "stamps": "Stamps",
-        "points": "Points",
-        "hybrid": "Hybrid"
-      }
-    },
-    "card": {
-      "title": "Loyalty Card",
-      "number": "Card Number",
-      "qr_code": "QR Code",
-      "enroll": "Enroll Customer",
-      "deactivate": "Deactivate Card"
-    },
-    "stamp": {
-      "title": "Stamps",
-      "add": "Add Stamp",
-      "redeem": "Redeem Reward",
-      "count": "{current} of {target}",
-      "until_reward": "{count} until reward"
-    },
-    "points": {
-      "title": "Points",
-      "earn": "Earn Points",
-      "redeem": "Redeem Points",
-      "balance": "{count} points",
-      "per_euro": "{points} points per euro"
-    },
-    "pin": {
-      "title": "Staff PINs",
-      "create": "Create PIN",
-      "edit": "Edit PIN",
-      "unlock": "Unlock PIN",
-      "locked": "PIN locked until {time}"
-    },
-    "wallet": {
-      "google": "Add to Google Wallet",
-      "apple": "Add to Apple Wallet"
-    },
-    "stats": {
-      "title": "Statistics",
-      "total_cards": "Total Cards",
-      "active_cards": "Active Cards",
-      "stamps_issued": "Stamps Issued",
-      "rewards_redeemed": "Rewards Redeemed"
-    },
-    "errors": {
-      "program_not_found": "Loyalty program not found",
-      "program_inactive": "Loyalty program is not active",
-      "card_not_found": "Loyalty card not found",
-      "card_inactive": "Loyalty card is not active",
-      "cooldown": "Please wait {minutes} minutes before next stamp",
-      "daily_limit": "Daily stamp limit of {limit} reached",
-      "insufficient_stamps": "Need {required} stamps, have {current}",
-      "insufficient_points": "Need {required} points, have {current}",
-      "pin_required": "Staff PIN is required",
-      "pin_invalid": "Invalid staff PIN",
-      "pin_locked": "PIN locked due to too many failed attempts"
+    "menu": {
+        "loyalty": "Loyalty",
+        "loyalty_programs": "Loyalty Programs",
+        "programs": "Programs",
+        "analytics": "Analytics",
+        "dashboard": "Dashboard",
+        "customer_cards": "Customer Cards",
+        "statistics": "Statistics"
     }
-  }
 }