LOW: Fix Load More button replacing items instead of appending

[Brad-Edwards]

Severity: Low (Quality L6)

`src/server/components/item-card.tsx:114` — HTMX `hx-swap="innerHTML"` replaces `#items-list` entirely with just the new page, losing previously loaded items. Users expect append behavior.

Recommendation: Change to `hx-swap="beforeend"` and adjust the target/response.