chore: enhance data source configuration and mock data handling

- Added support for mock data mode in the frontend by introducing a new environment variable in the Dockerfile and workflow configuration.
- Updated the settings page to conditionally display options based on the availability of mock data, improving user experience.
- Refactored data source logic to include a check for mock data availability, ensuring proper mode handling in the application.

Dockerfile.frontend

@@ -11,9 +11,11 @@ FROM deps AS build
 ARG BACKEND_INTERNAL_URL=http://backend:8000
 ARG NEXT_PUBLIC_BACKEND_URL=same-origin
 ARG NEXT_PUBLIC_DEFAULT_DATA_SOURCE=live
+ARG NEXT_PUBLIC_ALLOW_MOCK_DATA=false
 ENV BACKEND_INTERNAL_URL=$BACKEND_INTERNAL_URL
 ENV NEXT_PUBLIC_BACKEND_URL=$NEXT_PUBLIC_BACKEND_URL
 ENV NEXT_PUBLIC_DEFAULT_DATA_SOURCE=$NEXT_PUBLIC_DEFAULT_DATA_SOURCE
+ENV NEXT_PUBLIC_ALLOW_MOCK_DATA=$NEXT_PUBLIC_ALLOW_MOCK_DATA
 COPY packages/contracts packages/contracts
 COPY next.config.ts tsconfig.json postcss.config.mjs components.json ./
 COPY app app