fix(web): mock /api/auth/get-session in Dev login selector test

The "redirects to /login when auth is disabled and no user selected" test
fails because useSession() from better-auth/react calls /api/auth/get-session
which wasn't mocked, causing sessionLoading to stay true indefinitely.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/src/__tests__/App.test.tsx

@@ -150,6 +150,12 @@ describe("Dev login selector", () => {
           }),
         } as Response);
       }
+      if (url === "/api/auth/get-session") {
+        return Promise.resolve({
+          ok: true,
+          json: async () => ({ user: null }),
+        } as Response);
+      }
       return Promise.resolve({ ok: true, json: async () => [] } as Response);
     }) as unknown as typeof fetch;