Add friend: a pasted invite without https:// or /i/ fails with raw 'invite_not_found' #310

What happens

Sidebar + → Add friend: pasting 47-80-69-220.sslip.io/eWDDdBMIxLSZ (no https://, and the /i/ part missing; the real link is https://47-80-69-220.sslip.io/i/eWDDdBMIxLSZ) and clicking Accept invite shows the raw error:

Accepting invite failed: Bot Social join_invite: invite_not_found

Why

social/join-invite only strips a leading …/i/. Without /i/ the whole pasted text is sent to Bot Social's join_invite, which looks it up as the invite code (Bot Social itself only strips ^.*/i/), so it is never found. Then the error code reaches the UI as written; only relationship_exists and "used" were turned into sentences.

Expected

• The box takes a full link, a link without the scheme, a link whose /i/ is missing (host plus one bare token), a bare code, and the whole copied invite text.
• A pasted host that is not the configured server is never added to a bare code; the link is still tried, and the not-found message says it may come from another server.
• invite_not_found (and expired / revoked / own invite / blocked / rate limited) read as one short plain sentence, e.g. "This invite link wasn't found. It may be incomplete, expired, or already used. Ask your friend for a new link."
• No new buttons.