L17 Pakete: Stufen Basis/Profi, Lotse-Chat-Plätze und Kontingent

- Datenmodell: Tenant.tier (Default PROFI), lotseChatSeats, lotseChatHardLimit;
  Tabelle lotse_chat_seats (RLS, TENANT_MODELS, pii-fields), Index für die
  Monatszählung der Chat-Nachrichten (Migration 20260921100000_pakete)
- src/lib/plans.ts: Stufenregeln, 150 Chats je Platz, Mehrverbrauch in 100er-Paketen
- src/server/plan.ts: effektive Freischaltung = Stufe UND TenantModule, genutzt von
  requireModule, assertModuleEnabled, API, Sync (Offline-Op → rejected mit Klartext),
  Navigation, isLotseEnabled und planningAccess (Planung nur in Profi)
- Lotse-Chat: Platzprüfung (no_seat), Testphase ohne Platz, Kontingent mit
  hartem Limit (quota_exhausted); Platzvergabe durch den Mandanten-Admin
- Betreiber: Stufe/Plätze/hartes Limit im Mandantendetail mit Bestätigung
  und Plattform-Audit, Verbrauch laufender Monat/Vormonat, Stufe als Badge
- Demo-Seed: demo = Profi mit 3 Plätzen, demo2 = Basis
- Tests: test-pakete-{rules,gates,seats}

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

messages/en/lotse.json

@@ -317,11 +317,15 @@
       "transition_forbidden": "You lack the permission.",
       "not_editable": "The report has been submitted and can no longer be changed.",
       "reason_required": "The reason is missing.",
-      "use_billing_overview": "Only possible via the billing overview."
+      "use_billing_overview": "Only possible via the billing overview.",
+      "not_in_plan": "The Lotse is included in the Profi package and not activated for this company.",
+      "no_seat": "The Lotse chat is not activated for you yet – please ask the office.",
+      "quota_exhausted": "The company's chat quota for this month is used up."
     },
     "unavailable": {
       "title": "Lotse chat not available",
       "back": "Back to overview"
-    }
+    },
+    "quotaExhausted": "The company's chat quota for this month is used up. You can write again from next month – the office can help with questions."
   }
 }