feat(B-3): inventory block and Foundry item sync

Add inventory block type for character entity pages that displays
"Has Item" relations with quantity, equipped, and attuned metadata.
Includes Chronicle inventory widget (JS) and Foundry ItemSync module
for bidirectional item sync between Actor inventories and Chronicle
entity relations.

- Register "inventory" block in block_registry_core (addon: armory)
- Add blockInventory templ component as widget mount point
- Add "inventory" to default entity block types
- Create static/js/widgets/inventory.js Chronicle widget
- Create foundry-module/scripts/item-sync.mjs sync module
- Register ItemSync in Foundry module.mjs

https://claude.ai/code/session_01WJEjfBqjZaGatHiXXXDupo

Author: claude