feat(abonnements): paliers LLM Essentielle/Premium, admin modeles par forfait, statistiques revenus, emails marketing

- Gamme officielle : Essentielle (Pro) = deepseek-v4-flash, glm-5.3-flash,
  minimax-m3 ; Premium (Business) = claude-sonnet-5, deepseek-v4-pro, glm-5.3
- Routage reel : le modele employe suit le palier IA du forfait (reglages
  admin > defaut du plan), garde anti-croisement de palier
- Nouvelle page admin « Modeles & abonnements » (matrice forfaits/paliers,
  modele par defaut, catalogue OpenRouter)
- Statistiques enrichies : revenus (30 j + total), MRR estime, credits,
  liste d'attente, paliers utilises
- Nouvelle page admin « Marketing » : audiences avec compteurs, apercu,
  envoi test obligatoire, historique, desabonnement public + en-tetes
  List-Unsubscribe ; .gitignore pour les donnees d'execution
- Interface (accueil + tarifs) alignee sur la gamme, 13 langues completes
- Tests : routage par palier (fonction + tache), marketing, revenus en base

models/subscription.py

@@ -31,10 +31,24 @@ import os
 # NOTE: Stripe price IDs must be set via env vars in production.
 # Create products/prices in Stripe Dashboard: https://dashboard.stripe.com/products
 #
-# LLM models used (via OpenRouter — June 2026):
-#   Essentielle : deepseek/deepseek-chat  (DeepSeek V4/V3)
-#   Premium     : anthropic/claude-sonnet-4.6 (Claude Sonnet 4.6)
-#                 or google/gemini-3.5-flash (Gemini 3.5 Flash)
+# Official LLM ranges (via OpenRouter — September 2026). The model used per
+# translation is resolved from the plan's AI tier (admin settings > plan default):
+#   Essentielle (Pro plan)    : deepseek/deepseek-v4-flash, z-ai/glm-5.3-flash,
+#                               minimax/minimax-m3
+#   Premium     (Business)    : anthropic/claude-sonnet-5 (default),
+#                               alternatives deepseek/deepseek-v4-pro, z-ai/glm-5.3
+# A Pro user must never trigger a Premium model (see translate_routes).
+DEFAULT_AI_MODELS_ESSENTIAL = [
+    "deepseek/deepseek-v4-flash",
+    "z-ai/glm-5.3-flash",
+    "minimax/minimax-m3",
+]
+DEFAULT_AI_MODELS_PREMIUM = [
+    "anthropic/claude-sonnet-5",
+    "deepseek/deepseek-v4-pro",
+    "z-ai/glm-5.3",
+]
+
 PLANS = {
     PlanType.FREE: {
         "name": "Free",
@@ -97,7 +111,7 @@ PLANS = {
         "max_file_size_mb": 25,
         "max_chars_per_month": 2_000_000,
         "providers": ["google", "google_cloud", "openrouter"],
-        "ai_model_essential": "deepseek/deepseek-chat",
+        "ai_models_essential": list(DEFAULT_AI_MODELS_ESSENTIAL),
         "features": [
             "pricing.plans.pro.feat1",
             "pricing.plans.pro.feat2",
@@ -127,8 +141,8 @@ PLANS = {
         "max_file_size_mb": 50,
         "max_chars_per_month": 10_000_000,
         "providers": ["google", "google_cloud", "openrouter", "openrouter_premium", "openai", "zai"],
-        "ai_model_essential": "deepseek/deepseek-chat",
-        "ai_model_premium": "anthropic/claude-sonnet-4.6",
+        "ai_models_essential": list(DEFAULT_AI_MODELS_ESSENTIAL),
+        "ai_models_premium": list(DEFAULT_AI_MODELS_PREMIUM),
         "features": [
             "pricing.plans.business.feat1",
             "pricing.plans.business.feat2",