feat: Community shop — item catalog and admin management UI

Context

Communities should be able to run a shop where members can browse and eventually purchase items that go into their inventory. This issue covers the data model and the admin-facing item management UI. Purchase/payment flow is handled separately.

Acceptance Criteria

Admin (Community Owner/Mods)

• Community settings has a "Shop" section
• Admins can create shop items with: name, description, image (upload), price (currency + amount), stock limit (optional, null = unlimited), max-per-user limit (optional), active/inactive toggle
• Admins can edit and delete (or archive) existing items
• Items can be ordered/sorted for display
• Bulk enable/disable items

Member-Facing Shop

• Shop page at /community/:id/shop (or equivalent route)
• Lists active items with image, name, description, price, stock status ("In stock" / "X remaining" / "Out of stock")
• No purchase button in this ticket (placeholder "Buy" button is fine, wired up in payment issue)
• Empty state if no items

Technical Notes

• New DB table: shop_items
  • id, community_id (FK), name, description, image_url, price_cents (integer — avoid float), currency (default usd), stock (nullable integer), max_per_user (nullable integer), sort_order, active, sponsor_only (boolean, default false — wired up in gating issue), created_at, updated_at, deleted_at (soft delete)
• Store price in smallest currency unit (cents) to avoid floating point rounding
• Use existing image upload infrastructure for item images
• Align item model with existing inventory/trait item model if one exists — shop items should eventually map to inventory item types

Dependencies

None — foundational, no prerequisites.

Future Scope

• Sponsor-only item gating (separate issue, adds sponsor_only flag to this schema)
• Stripe checkout integration (separate issue)
• Bundle/pack items

Start by locating the community settings and /community/:id/shop entry points, then inspect the existing image upload infrastructure and inventory/trait item model. Define the shop_items data model around the listed fields and follow the project’s conventions for admin and member-facing UI. Done means the admin management actions and member shop states in the acceptance criteria are covered, without purchase or sponsor gating.