Square every corner, enlarge the main surfaces and add a to-do list

Rounded rectangles and round controls are now square across the app; only
status dots, glows, the sun, rings and the breathing circle stay round.
Cards, rows, thumbnails, featured cards, category tiles, the standing card
and the nav are larger. Home gets a quick To-do list kept on the device
(TodoItem in InternalMemory), seeded with sample items in mock mode.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KhQh614DMeYoQEH9SoMRUw

frontend/lib/Grounded/see/login/LoginState.dart

@@ -107,8 +107,8 @@ class LoginState extends State<Login> implements ConnectLogin {
             decoration: BoxDecoration(
               color: colorPrimaryLight,
               borderRadius: const BorderRadius.only(
-                topLeft: Radius.circular(28),
-                topRight: Radius.circular(28),
+                topLeft: Radius.zero,
+                topRight: Radius.zero,
               ),
             ),
             clipBehavior: Clip.antiAlias,