Update BTCPay integration with production credentials and deployment documentation

- Updated API key and Store ID to production values
- Added comprehensive deployment documentation
- Fixed invoice creation to use GBP (fiat) currency
- Documented successful production deployment status
- Added manual deployment instructions
- Updated CLAUDE.md with latest integration fixes

Production Status:
- BTCPay connection working with v2.2.1
- Store "Shop" configured with ID: CvdvHoncGLM7TdMYRAG6Z15YuxQfxeMWRYwi9gvPhh5R
- Invoice creation functional (wallets need BTCPay-side configuration)

🤖 Generated with [Claude Code](https://claude.ai/code)

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

LittleShop/appsettings.Hostinger.json

@@ -0,0 +1,46 @@
+{
+  "ConnectionStrings": {
+    "DefaultConnection": "Data Source=/app/data/littleshop.db"
+  },
+  "Jwt": {
+    "Key": "YourSuperSecretKeyThatIsAtLeast32CharactersLong!",
+    "Issuer": "LittleShop",
+    "Audience": "LittleShop",
+    "ExpiryInHours": 24
+  },
+  "BTCPayServer": {
+    "BaseUrl": "https://thebankofdebbie.giize.com",
+    "ApiKey": "db920209c0101efdbd1c6b6d1c99a48e3ba9d0de",
+    "StoreId": "CvdvHoncGLM7TdMYRAG6Z15YuxQfxeMWRYwi9gvPhh5R",
+    "WebhookSecret": "your-webhook-secret-here"
+  },
+  "RoyalMail": {
+    "ClientId": "",
+    "ClientSecret": "",
+    "BaseUrl": "https://api.royalmail.net/",
+    "SenderAddress1": "SilverLabs Ltd, 123 Business Street",
+    "SenderCity": "London",
+    "SenderPostCode": "SW1A 1AA",
+    "SenderCountry": "United Kingdom"
+  },
+  "WebPush": {
+    "VapidPublicKey": "BMc6fFJZ8oIQKQzcl3kMnP9tTsjrm3oI_VxLt3lAGYUMWGInzDKn7jqclEoZzjvXy1QXGFb3dIun8mVBwh-QuS4",
+    "VapidPrivateKey": "dYuuagbz2CzCnPDFUpO_qkGLBgnN3MEFZQnjXNkc1MY",
+    "Subject": "mailto:admin@littleshop.local"
+  },
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning",
+      "BTCPayServer": "Debug"
+    }
+  },
+  "AllowedHosts": "*",
+  "Kestrel": {
+    "Endpoints": {
+      "Http": {
+        "Url": "http://0.0.0.0:8080"
+      }
+    }
+  }
+}