feat: add cart, providers, swag modules — Phase 4 cosmolocal commerce
Port the three cosmolocal print-on-demand services (rCart, Provider Registry,
Swag Designer) into the unified rSpace module system. Each module includes
Hono API routes, folk-* web components, DB schemas, and standalone servers.
- Cart: catalog ingest, orders with state machine, x402 detection, rFunds flow deposit
- Providers: 6 seeded providers, earthdistance proximity queries, capability matching
- Swag: product templates (sticker/poster/tee), Sharp image processing, artifact envelopes
- DB: cube + earthdistance extensions, rcart + providers schemas
- Docker: swag-artifacts volume, payment-network for flow service
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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