refactor: enhance TimerPage layout and functionality; update theme and tokens for improved design consistency

- Refactored TimerPage component to improve layout and user experience.
- Updated theme configuration to utilize design tokens for better maintainability.
- Introduced new tokens for colors and typography to align with design principles.
- Simplified state management and improved timer functionality.
- Enhanced accessibility and responsiveness of UI elements.

backend/tests/conftest.py

@@ -12,6 +12,9 @@ import tempfile
 
 import pytest
 
+# Before anything imports the settings: no `.env`, ever. A developer's real
+# file would otherwise point the suite at live Jira, Telegram and laundry.
+os.environ["KADENCE_NO_DOTENV"] = "1"
 os.environ.setdefault("DATABASE_URL", "sqlite:///" + tempfile.mktemp(suffix=".db"))
 os.environ["SCHEDULER_ENABLED"] = "false"
 os.environ["TELEGRAM_BOT_ENABLED"] = "false"