docs: add CLAUDE.md with project guidance for Claude Code

Add comprehensive documentation file to help Claude Code understand the codebase structure, build commands, architecture, and development workflow for the nf-core stats dashboard project.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: edmundmiller

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+This is the nf-core stats dashboard project. It consists of two main components:
+1. **Evidence.dev frontend** - A data visualization dashboard for nf-core statistics
+2. **DLT data pipelines** - Python pipelines that collect data from GitHub, Slack, and Twitter APIs
+
+## Build Commands
+
+### Frontend (Evidence.dev)
+```bash
+npm install          # Install dependencies
+npm run sources      # Refresh data sources
+npm run dev          # Start development server
+npm run build        # Build for production
+npm run test         # Run tests (builds the project)
+```
+
+### Data Pipelines (Python/DLT)
+```bash
+cd pipeline
+uv run python github_pipeline.py  # Run GitHub stats collection
+uv run python slack_pipeline.py   # Run Slack stats collection
+```
+
+## Architecture
+
+### Data Flow
+1. **Data Collection**: Python DLT pipelines (`pipeline/`) fetch data from external APIs (GitHub, Slack)
+2. **Data Storage**: Data is stored in MotherDuck (cloud DuckDB) database `nf_core_stats_bot`
+3. **Data Visualization**: Evidence.dev reads from MotherDuck and renders interactive dashboards
+
+### Key Directories
+- `pipeline/` - DLT data pipelines for collecting stats
+- `pages/` - Evidence.dev markdown pages with SQL queries and visualizations
+- `sources/` - Database connection configurations
+- `.github/workflows/` - GitHub Actions for daily pipeline runs and Netlify builds
+
+### Database Schema
+The MotherDuck database contains tables for:
+- `github_traffic_stats` - Repository views and clones
+- `github_contributor_stats` - Contributor activity by week
+- `github_issue_stats` - Issues and pull requests
+- `slack_messages` - Slack channel message counts
+- `slack_members` - Slack member statistics
+
+### Environment Variables
+Required secrets for pipelines (set in GitHub Actions or local `.env`):
+- `SOURCES__GITHUB_PIPELINE__GITHUB__API_TOKEN` - GitHub personal access token
+- `SOURCES__SLACK_PIPELINE__SLACK__API_TOKEN` - Slack user token
+- `DESTINATION__MOTHERDUCK__CREDENTIALS__DATABASE` - MotherDuck database name
+- `DESTINATION__MOTHERDUCK__CREDENTIALS__PASSWORD` - MotherDuck token
+
+## Development Notes
+
+- Evidence pages use SQL queries embedded in markdown to fetch data
+- The GitHub pipeline uses incremental loading with merge strategy to update existing records
+- Pipelines run daily via GitHub Actions and are monitored with runitor
+- The frontend is deployed to Netlify and rebuilt daily after pipeline runs