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/routine/StepEditorState.dart

@@ -67,8 +67,8 @@ class StepEditorState extends State<StepEditor> {
         decoration: const BoxDecoration(
           color: colorSheetBackground,
           borderRadius: BorderRadius.only(
-            topLeft: Radius.circular(28),
-            topRight: Radius.circular(28),
+            topLeft: Radius.zero,
+            topRight: Radius.zero,
           ),
         ),
         child: SingleChildScrollView(
@@ -234,7 +234,7 @@ class StepEditorState extends State<StepEditor> {
       padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 12),
       decoration: BoxDecoration(
         color: kindBackground(widget.kind),
-        borderRadius: BorderRadius.circular(12),
+        borderRadius: BorderRadius.zero,
       ),
       child: Row(
         children: [