Captures page: the recording checklist with one start/end button

Steps come from a bundled copy of contracts checklists/ (assets/contracts/,
refreshed by tool/sync-contracts.sh), not from Dart.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

pubspec.yaml

@@ -57,10 +57,9 @@ flutter:
   # the material Icons class.
   uses-material-design: true
 
-  # To add assets to your application, add an assets section, like this:
-  # assets:
-  #   - images/a_dot_burr.jpeg
-  #   - images/a_dot_ham.jpeg
+  # Exact copies of contracts files (tool/sync-contracts.sh); crosscheck verifies them.
+  assets:
+    - assets/contracts/checklists/
 
   # An image asset can refer to one or more resolution-specific "variants", see
   # https://flutter.dev/to/resolution-aware-images