Move proposal creation draft URL to cloud

[NoahSaso]

Right now you can copy the current proposal creation form as a URL, but it's really long because it copies the entire form state into a base64-encoded query parameter.

Really this should upload to some Cloudflare Worker and update it, letting others with the link update it as well.

A simple version would be to upload to IPFS each time they press the copy link button, but that might be slow, would waste our IPFS storage space, and would require people to keep sending links back and forth. Suboptimal.

[NoahSaso]

i went the suboptimal route for now, uploading data to IPFS (d62c5bb). i'm leaving this issue open because this should definitely still be built out more