Relay UI already shows a tenant's inbox + sent mails. Add a parallel
view for collaborative bucket cards the logged-in tenant is a member
of, so activity on shared boards is visible without needing the hyprcrd
client open.
New `GET /api/collab-inbox` endpoint (session-auth only) decrypts
payloads with the inter-tenant key and returns title + preview + author
+ bucket metadata. UI restructures the compose view into editor + right
sidebar stacking inbox → shared → sent, and polls all three on the
existing 15s tick.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
thandClaude Opus 4.6
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