Add wish list feature with drag-and-drop sorting

[Copilot]

Adds a persistent wish list where users can track desired items with a title, optional URL, and optional approximate price — sortable via drag-and-drop.

Storage (src/storage.ts)

• New WishItem interface: id, title, url?, price?, order, createdDate
• wishList: WishItem[] added to AppData; initialized to [] in createInitialData()
• New StorageManager methods: addWishItem, updateWishItem, deleteWishItem, getWishItems, reorderWishItems

UI (index.html)

• New 🎁 Wish List nav tab (between Shop and Finances)
• Tab section with item list, add button, and modal form (title required; URL and price optional)

App Logic (src/app.ts)

• renderWishList() renders items with native HTML5 drag-and-drop; drop reorders via reorderWishItems()
• Full modal CRUD: openWishItemModal, saveWishItem, deleteWishItem
• dragSrcWishId cleared on dragend to prevent stale drag state

Styles (css/styles.css)

• Wish list item layout with drag handle, .dragging opacity, and .drag-over highlight border

Tests (tests/storage.test.ts)

• 7 new unit tests covering add, get (sorted), update, delete (with re-index), and reorder

Original prompt

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This section details on the original issue you should resolve

<issue_title>Implement a new wish list</issue_title>
<issue_description>The app needs a wish list feature implemented that will have a title, optional url to a listing, and optional approximate price. The user should be able to sort their list by dragging and dropping their items</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Implement a new wish list #26

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