WIP: Ylide forum

[ElKornacio]

WIP: This update incorporates decentralized forum functionality into Blockscout.

It introduces @ylide/sdk and @ylide/ethereum as dependencies, alongside two new environment variables:

1. NEXT_PUBLIC_IS_FORUM_SUPPORTED - a boolean feature flag
2. NEXT_PUBLIC_FORUM_INDEXER_URL - the URL of the forum indexer backend.

New variables are documented in ENVS.md.

The integration operates through context hooks. The key components are now implemented:

1. Forum topics, threads, and replies
2. Direct messages - encrypted end-to-end chats
3. Authorization management - retrieval and storage of communication keys

Work in progress:

1. Code refactoring to better align with the project's overall code style.
2. Dockerization and provisioning of the backend.
3. Possible existence of bugs.

The primary goal of this PR is to deploy this branch to the staging domain for functionality validation in a production-style environment.