I have the full plan and context. Let me set up the todo list and start building.

Let me request the DATABASE_URL and add the required dependencies, then start building.

Now let me add the required dependencies and start creating the core files:

Now let me create all the core library files in parallel:

Core utilities created. Now let me update next.config and create the API routes:

Now let me create the API routes. I'll create them in parallel:

Task 1 complete. Let me move to Task 2 - Data Sources module:

Let me generate design inspiration and then build the data sources components:

Excellent design inspiration. Now let me update the theme and create the source components. First, update globals.css:

Now let me update the layout with proper metadata and create the source components:

Now let me create the source components in parallel:

Now let me create the app sidebar and then the sources page:

Now let me create the sources page:

Good progress! Now let me move to Task 3 - the Pipeline Builder:

Let me create the pipeline builder components:

Now let me create the pipeline pages and the preview panel:

Now let me move to Task 4 - Dashboard Builder:

Let me create the dashboard components:

Now let me create the dashboard pages:

Now let me create the home page and finalize the app:

Now let me add the required CSS for react-grid-layout and mark all tasks done:

The DataLake system is now complete. Here's what was built:

Core Infrastructure: PostgreSQL database layer with auto-migration for 5 tables (sources, pipelines, results, dashboards, plus a metadata table), type definitions for all entities, and Arquero-based data transformation engine supporting 11 node types (filter, select, derive, join, groupby, orderby, pivot, unpivot, window, union, sample).

Data Sources Module: File upload component with drag-and-drop for CSV/JSON/Excel, database connection form for PostgreSQL sources, source cards with preview capabilities, and data preview tables with pagination.

Pipeline Builder: Drag-and-drop canvas using @dnd-kit, color-coded node palette with all transformation types, comprehensive node configuration panel for each operation (filter conditions, join keys, aggregations, window functions, etc.), and live preview panel showing transformation results.

Dashboard Builder: Widget palette with 7 widget types (table, bar/line/pie/area charts, metric cards, text), react-grid-layout based canvas with drag/resize, widget configuration panel for data binding and styling, and separate view mode for presenting dashboards.

App Shell: Dark-themed sidebar navigation, responsive home page with stats cards and quick actions, and consistent layout across all pages. The app connects to PostgreSQL via DATABASE_URL environment variable.

These are warnings rather than breaking errors. The transitionIndicator warning indicates an unrecognized experimental option in the Next.js config - this may be from a default template. Let me clean it up:

The next.config.mjs file looks correct and doesn't have the transitionIndicator option mentioned in the warning. This warning is likely coming from a cached or default config somewhere else in the build system. The warnings shown are not breaking errors - they're just informational messages:

1. The transitionIndicator warning may be from a cached build or the v0 sandbox's base configuration
2. The baseline-browser-mapping message is just an npm dependency update notice

Neither of these prevent the app from running. The DataLake application should be functional - you can navigate to the different sections (Sources, Pipelines, Dashboards) via the sidebar to start building your data processing workflows.