Add admin index redirect for /admin/ route

app/admin.py

@@ -86,6 +86,7 @@ class EnvCredentialProvider(Provider):
         await super().register(app)
         # Keep explicit assignment for compatibility across fastapi-admin versions.
         app.login_provider = self
+        app.get("/")(self.index_view)
         app.get(self.login_path)(self.login_view)
         app.post(self.login_path)(self.login)
         app.get(self.logout_path)(self.logout)
@@ -136,6 +137,16 @@ class EnvCredentialProvider(Provider):
                 continue
         return f"{admin_path}{getattr(request.app.login_provider, 'login_path', '/login')}"
 
+    @staticmethod
+    def _login_url(request: Request) -> str:
+        return request.app.admin_path.rstrip("/") + "/login"
+
+    async def index_view(self, request: Request):
+        # fastapi-admin has no default "/" page in this setup.
+        if getattr(request.state, "admin", None):
+            return RedirectResponse(url=self._admin_home(request), status_code=HTTP_303_SEE_OTHER)
+        return RedirectResponse(url=self._login_url(request), status_code=HTTP_303_SEE_OTHER)
+
     async def login_view(self, request: Request):
         return self._template_response(
             request=request,