Allow users to use custom fonts in Fancy Text

[bobnik]

Currently, Sandify ships with a curated set of fonts. Users can request we add additional fonts, but each addition requires a code change. This feature lets users upload any TTF or OTF font file directly in the app. The font appears in the Font dropdown and can be used immediately with Fancy Text.

• Upload via file picker in the Font dropdown ("Upload font..." option)
• Uploaded fonts persist in browser storage (IndexedDB) across sessions
• Supports TTF and OTF formats

Custom fonts are stored locally in the browser - just like fonts installed on a computer. If someone shares a .sandify file that uses a custom font, recipients who don't have that font will see a fallback (with a warning), a similar behavior as Adobe Illustrator or other design tool.

User experience

1. Create a Fancy Text layer
2. Open the Font dropdown
3. Select "Upload font..." at the bottom
4. Pick a .ttf or .otf file
5. Font loads and is automatically selected
6. Use it like any other font