Add Notes feature

[Copilot]

Users need a way to create, view, edit, and delete multiple freeform notes within the app.

Storage (src/storage.ts)

• New Note interface: id, title, content, createdDate, updatedDate?
• notes: Note[] added to AppData (initialized empty)
• CRUD methods: addNote, updateNote, deleteNote, getNotes — notes sorted by most recently updated

UI (index.html)

• "📝 Notes" nav tab
• Card-grid notes list with + Add Note button
• Modal with title input + textarea for content; supports add/edit/delete

App logic (src/app.ts)

• currentEditingNoteId state, event listeners wired to new buttons
• renderNotes, renderNoteItem, openNoteModal, closeNoteModal, saveNote, deleteNote
• HTML in rendered note titles and previews escaped via existing escapeHtml to prevent XSS

Styles (css/styles.css)

• Responsive card-grid layout for note cards with hover effects

Tests (tests/storage.test.ts)

• 7 unit tests covering CRUD, default values, sort order, and updatedDate stamping

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add note feature</issue_title>
<issue_description>Users would like a new feature in the app to type notes. Multiple notes should be supported and the user can delete individual notes when needed</issue_description>

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

• Fixes Add note feature #38

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