Accept `NotionMediaItem[]` directly in `fetchItunesItems` instead of a hand-mapped `iTunesListItem` interface

[ooloth]

Why

The private iTunesListItem interface in fetchItunesItems is structurally identical to a subset of NotionMediaItem, so every caller must manually map NotionMediaItem fields to the narrower interface — a redundant transformation that the type system could eliminate.

Current state

io/itunes/fetchItunesItems.ts lines 9–13 define interface iTunesListItem { date: string; id: number; name: string }. app/likes/page.tsx maps NotionMediaItem to this interface at lines 24, 28, 32: i => ({ id: i.appleId, name: i.name, date: i.date }) — once per media category.

Ideal state

• fetchItunesItems accepts NotionMediaItem[] directly (or a shared named subtype).
• The appleId field is used without renaming inside the function.
• Callers pass items without hand-mapping fields; the per-category transformations at lines 24, 28, 32 are removed.

Starting points

• io/itunes/fetchItunesItems.ts — lines 9–13 (the iTunesListItem interface) and the function signature
• app/likes/page.tsx — lines 24, 28, 32 (the per-category mapping transformations to remove)

QA plan

1. Open io/itunes/fetchItunesItems.ts and verify the function signature accepts NotionMediaItem[] with no intermediate mapping type.
2. Open app/likes/page.tsx and verify the per-category i => ({ id: i.appleId, ... }) mappings are gone.
3. Run tsc --noEmit — expect no type errors.

Done when

fetchItunesItems accepts NotionMediaItem[] directly and no iTunesListItem interface or equivalent mapping transformation exists in the codebase.