Arweave/Permaweb integration

Goals

• Add checkbox to composer that allows users to "Post to Permaweb" -- this would limit composing options to only status or blogs until Arweave 2.0 with video support drops.
• Activity post entities would post both to Minds database and Arweave with an indicator/icon that it is on the Permaweb.
• Add filter for permaweb content in discovery.
• Decide whether to use arweave.net or Minds gateway.
• Describe architecture.

Key Management

• Option 1 - Minds manages keys for users. Minds buys Arweave tokens and pays for each post. Minds charges Minds tokens to user posting to Permaweb in exchange.
• Option 2 - Minds users manage keys themselves. They sync their Minds login and receive their own key for download, which needs to be sent with the transaction (?). They have their own balance of Arweave tokens and pay for posting themselves.
• Option 3 - Offer both options