feat: Support external font URLs in Fonts Manager (preview + dropdown)

[vianmora]

Problem

When using custom fonts (e.g. self-hosted on a CDN, or loaded via a @font-face in Custom Code), there is currently no way
to:

• See the font previewed in the builder canvas
• Have the font appear in the Font Family dropdown

The only workaround is to upload the font files as assets, which counts against the 50-asset-per-project limit. For font
families with many weights/styles (e.g. a variable font with 50+ files), this limit is immediately exhausted by a single
typeface.

Expected behavior

Users should be able to declare an external font (family name + URL) directly in the Fonts Manager, without uploading the
actual files. The declared font should:

1. Appear in the Font Family dropdown alongside uploaded and system fonts
2. Be previewed in the builder canvas (via a generated @font-face rule)
3. Be included in the published site's CSS output

Proposed implementation

1. Add an externalFonts field to ProjectMeta in packages/sdk/src/schema/pages.ts:
   { family: string, url: string, weight?: number, style?: "normal" | "italic" }[]
2. Extend addFontRules() in packages/sdk/src/css.ts to also process externalFonts
3. Pass externalFonts to addFontRules in the canvas (apps/builder/app/canvas/shared/styles.ts)
4. Include external fonts in toItems() (fonts-manager/item-utils.ts) so they appear in the dropdown
5. Add a small "Add external font" UI in the Fonts Manager panel

No database migration needed — externalFonts would be a new optional JSON field in the existing projectMeta blob.

Alternatives considered

• Using Custom Code (head) to inject a or @font-face — works on the published site but the font is invisible in the
  builder canvas and not selectable in the dropdown
• Uploading all font files — hits the asset limit quickly for large font families

[kof]

If you have 50 fonts the site is going to be extremely slow, normal websites have up to 3. Ideally not more than 2. What's the reason having so many fonts?

[TrySound]

variable font with 50+ files

Variable font is about single file for all font variations, so using it you should not hit the limit.

https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Fonts/Variable_fonts

[vianmora]

No, I don't need 50 fonts ^^ I was just trying to implement a font (DM sans) and by importing everything in the zip file without really looking at the details of each font (I thought, I'll just choose them directly on the canvas), I saw the limit on the assets. So I tried importing with the CDN, but I didn't get the rendering in the canvas, hence this issue ^^ but indeed, it's more of a minor inconvenience than a real problem 😊

and yes, thanks TrySound, i’ll try Variable fonts 😊