Grant proposal submission form

[carletex]

URL /submit-grant

• check if member is from BG (API endpoint)
• sign message to backend
• backend verify /api/submit-grant (this can be a "service")
• save to firebase (status: pending)

Fields: title, description, expected amount (?? it could be a dropdown: 0.25 / 0.5 / 1)

Grant firestore fields:

• Grant meta (title, description, builder)
• timestamp
• status
• amount??