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/system/sessionexpired/SessionExpiredState.dart

@@ -71,7 +71,7 @@ class SessionExpiredState extends State<SessionExpired>
                   alignment: Alignment.center,
                   decoration: BoxDecoration(
                     color: colorWhite.withValues(alpha: 0.10),
-                    borderRadius: BorderRadius.circular(18),
+                    borderRadius: BorderRadius.zero,
                   ),
                   child: Icon(CupertinoIcons.lock_fill,
                       size: 24, color: colorWhite),

frontend/lib/Grounded/see/system/updateme/UpdateMeState.dart

@@ -68,7 +68,7 @@ class UpdateMeState extends State<UpdateMe> implements ConnectUpdateMe {
                   alignment: Alignment.center,
                   decoration: BoxDecoration(
                     color: colorWhite.withValues(alpha: 0.10),
-                    borderRadius: BorderRadius.circular(18),
+                    borderRadius: BorderRadius.zero,
                   ),
                   child: Icon(CupertinoIcons.arrow_up_circle_fill,
                       size: 24, color: colorWhite),