aba32b18

By: Michael Lynch <git@mtlynch.io>

Add ItemName type for validated grocery item names

Introduces a typed ItemName struct in types/grocery.go that rejects
empty or whitespace-only names and strips leading/trailing whitespace.
Changes GroceryItem.Name from string to ItemName and updates all
references in the sqlite store. Adds unit tests.

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