feat(relay): make NIP-11 name and description configurable

[A-PachecoT]

Problem

A self-hosted relay is a distinct workspace to the people using it, but every instance introduces itself as "Buzz Relay" — the product's name, not the operator's:

// crates/buzz-relay/src/nip11.rs
name: "Buzz Relay".to_string(),
description: "Buzz — private team communication relay".to_string(),

Clients surface this string, so an operator running Buzz for their own team has no way to make the deployment read as theirs. The Desktop's Edit Community → Name field looks like the answer but only writes to localStorage, so the NIP-11 document — what every other client reads — still says "Buzz Relay".

We hit this running Buzz for our own company: the workspace icon propagates fine via the kind:9033 command, so the deployment ends up showing our logo next to someone else's name.

Change

Adds RELAY_NAME and RELAY_DESCRIPTION, read at NIP-11 build time.

• Defaults to the current strings, so no existing deployment changes behaviour.
• Blank or whitespace-only values fall back to the default rather than advertising an empty name.
• Values are trimmed.

Kept deliberately small: two env vars and one helper, no config-struct plumbing, matching how pairing_relay_url and icon already reach this function.

Testing

relay_name_and_description_come_from_env_and_ignore_blanks covers unset (defaults), set-and-trimmed, and blank-falls-back.

The test was verified to have teeth by mutating the fix back to the hardcoded string and confirming it fails:

test nip11::tests::relay_name_and_description_come_from_env_and_ignore_blanks ... FAILED
assertion `left == right` failed

Restored, the full nip11 module passes:

test result: ok. 17 passed; 0 failed

cargo fmt --check and cargo clippy -p buzz-relay --lib are clean.

Notes

Happy to move this into Config instead if you'd prefer the values to travel with the rest of the relay configuration — this shape just mirrors what the surrounding code already does.