fix(app): fix Notes editor formatting and title issues

[comppaz]

Summary

• Fix bullet list, numbered list, and blockquote buttons not working
• Fix H2/H3 heading differentiation (H3 now visually distinct)
• Fix title horizontal scrolling (auto-resizing textarea)
• Fix Enter key in title to move focus to editor

Root Cause

The .ProseMirror CSS rules were inside @layer components, causing Tailwind's JIT compiler to purge them since .ProseMirror is a class added dynamically by TipTap (not detected in source files).

Changes

• index.css: Moved all .ProseMirror rules outside @layer components to prevent purging
• index.css: Updated H3 styling (1.125rem, font-weight 500) to differentiate from H2
• NoteEditor.tsx: Changed title <input> to <textarea> with auto-resize
• NoteEditor.tsx: Added Enter key handler to focus editor from title

Test plan

• Open Notes editor
• Click bullet list button → should show bullet points
• Click numbered list button → should show numbers
• Click blockquote button → should show indented quote with border
• Create H2 and H3 → H3 should be visibly smaller/lighter
• Type long title → should wrap to multiple lines
• Press Enter in title → focus should move to editor

Closes #92