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>

CHANGELOG.md

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+# Changelog
+
+All notable changes to BeanFlows are documented here.
+
+## [Unreleased]
+
+### Added
+- **Coffee analytics dashboard** — Chart.js visualizations for global supply/demand time series, stock-to-use ratio trend, top producing countries bar chart, and YoY production change table
+- **Country comparison page** — Multi-select country picker with metric selector and overlay line chart at `/dashboard/countries`
+- **DuckDB data access layer** (`web/src/beanflows/analytics.py`) — Async bridge to read-only DuckDB via `asyncio.to_thread()` with 7 domain query functions and metric allowlist for injection prevention
+- **Commodity REST API** — `GET /api/v1/commodities`, `/commodities/<code>/metrics`, `/commodities/<code>/countries`, `/commodities/<code>/metrics.csv` (CSV export)
+- **BeanFlows plan tiers** — Free (coffee, 5yr history), Starter (full history, CSV, API), Pro (all 65 commodities, unlimited API)
+- **Landing, features, and pricing pages** rewritten for coffee market intelligence positioning
+- **Health check** now verifies both SQLite and DuckDB connectivity
+- **Admin panel** shows commodity count and data year range from DuckDB
+- **Docker** config updated with DuckDB volume mount
+- **Tests** — `test_dashboard.py` (8 tests), `test_api_commodities.py` (8 tests), analytics mock fixture in conftest
+
+### Fixed
+- **Pipeline time granularity** — Added `market_year` to GROUP BY in `cleaned.psdalldata__commodity_pivoted` and carried through to `serving.commodity_metrics`. Previously summed across all market years, making per-year metrics meaningless.
+
+### Removed
+- `items` table, FTS virtual table, and triggers from schema (boilerplate domain entity)
+- Items CRUD from API routes
+- Items count from dashboard stats
+
+### Changed
+- `PLAN_FEATURES` updated from generic (`basic`, `export`) to domain-specific (`dashboard`, `coffee_only`, `all_commodities`, `full_history`, `export`, `api`)
+- `PLAN_LIMITS` changed from `items`/`api_calls` to `commodities`/`history_years`/`api_calls`
+- API now requires Starter or Pro plan (free plan gets 403)
+- Dashboard routes and API routes import analytics module (not individual functions) for testability
+- Billing tests updated to match new feature and limit names