add: pricing tiers configuration

pricing.json

@@ -0,0 +1,51 @@
+{
+  "tiers": {
+    "free": {
+      "name": "Free",
+      "price_monthly": 0,
+      "requests_per_day": 25,
+      "models": ["chatgpt-5"],
+      "features": ["basic-chat"],
+      "stripe_price_id": null,
+      "gumroad_product_id": null
+    },
+    "pro": {
+      "name": "Pro",
+      "price_monthly": 9.99,
+      "requests_per_day": 500,
+      "models": ["all"],
+      "features": ["basic-chat", "smart-routing", "tools", "priority-queue"],
+      "stripe_price_id": "STRIPE_PRO_PRICE_ID",
+      "gumroad_product_id": "GUMROAD_PRO_PRODUCT_ID"
+    },
+    "ultra": {
+      "name": "Ultra",
+      "price_monthly": 29.99,
+      "requests_per_day": 5000,
+      "models": ["all", "image-gen"],
+      "features": ["basic-chat", "smart-routing", "tools", "priority-queue", "image-generation", "image-editing"],
+      "stripe_price_id": "STRIPE_ULTRA_PRICE_ID",
+      "gumroad_product_id": "GUMROAD_ULTRA_PRODUCT_ID"
+    },
+    "enterprise": {
+      "name": "Enterprise",
+      "price_monthly": 99.99,
+      "requests_per_day": -1,
+      "models": ["all", "image-gen", "dedicated"],
+      "features": ["basic-chat", "smart-routing", "tools", "priority-queue", "image-generation", "image-editing", "sla", "custom-models", "dedicated-gpu"],
+      "stripe_price_id": "STRIPE_ENTERPRISE_PRICE_ID",
+      "gumroad_product_id": "GUMROAD_ENTERPRISE_PRODUCT_ID"
+    }
+  },
+  "payg": {
+    "price_per_request": 0.001,
+    "min_topup": 5.00
+  },
+  "providers": {
+    "stripe": {"enabled": true, "supports": ["subscription", "one-time"]},
+    "paypal": {"enabled": true, "supports": ["subscription", "one-time"]},
+    "coinbase": {"enabled": true, "supports": ["one-time", "crypto"]},
+    "square": {"enabled": true, "supports": ["one-time"]},
+    "gumroad": {"enabled": true, "supports": ["subscription", "one-time"]}
+  }
+}