Delete a font

Adds a font your templates can use. Send `multipart/form-data` with a `file` part, or JSON with `filename` and `content_base64`. Fonts are **team-level**: once uploaded, every template in the team can name it. Re-uploading the same filename replaces it. The response carries `family` — the name read out of the file itself, and **that exact string is what goes in `fontFamily` on a text component**. It is usually not the filename: `Anton-Regular.ttf` declares the family `Anton`. `.ttf` and `.otf` only, 10MB maximum. A variable font will not register — instance it to a static weight first. A file with no readable family name is rejected, because the renderer would never apply it.