Add BeanFlows MVP: coffee analytics dashboard, API, and web app

- Fix pipeline granularity: add market_year to cleaned/serving SQL models
- Add DuckDB data access layer with async query functions (analytics.py)
- Build Chart.js dashboard: supply/demand, STU ratio, top producers, YoY table
- Add country comparison page with multi-select picker
- Replace items CRUD with read-only commodity API (list, metrics, countries, CSV)
- Configure BeanFlows plan tiers (Free/Starter/Pro) with feature gating
- Rewrite public pages for coffee market intelligence positioning
- Remove boilerplate items schema, update health check for DuckDB
- Add test suite: 139 tests passing (dashboard, API, billing)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/.dockerignore

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+.venv/
+__pycache__/
+*.pyc
+*.pyo
+.git/
+.gitignore
+.env
+.env.*
+*.db
+*.db-shm
+*.db-wal
+data/
+backups/
+.ruff_cache/
+.pytest_cache/
+.vscode/
+.idea/