Persist relative return-to path for post-login redirect

Co-Authored-By: Codex <codex@openai.com>

tests/views/MainContainerGuard.test.js

@@ -91,4 +91,15 @@ describe('MainContainer beforeRouteEnter', () => {
 
     expect(next).toHaveBeenCalled();
   });
+
+  it('stores a relative return-to path when redirecting to login', async () => {
+    window.history.replaceState({}, '', '/discover/log/1/map?view=summary#node-2');
+
+    await callGuard();
+
+    const redirectArg = next.mock.calls[0][0];
+    const returnTo = redirectArg.query['return-to'];
+
+    expect(atob(returnTo)).toBe('/discover/log/1/map?view=summary#node-2');
+  });
 });