fix(backend): allow https://sportiq-tennis.vercel.app in CORS

Author: kr1shnasomani

backend/app/settings.py

@@ -16,6 +16,8 @@ class Settings(BaseSettings):
         "https://*.onrender.com",
         # Common Vercel preview and production domains (set exact domain via env for best security)
         "https://*.vercel.app",
+        # Explicit project domain (ensure CORS works even if regex fails on some hosts)
+        "https://sportiq-tennis.vercel.app",
     ], alias="ALLOWED_ORIGINS")
 
     # Pydantic v2 settings configuration