Agent sharing via link

[isTravis]

• Agent share link — collection owners can generate a short-lived (1 hour) API key and share it with an AI agent. The /agent/:token page describes the collection's schema, current state, and the full negotiate protocol so any AI chat can write structured updates back. A modal in the collection sidebar lets owners copy the link or a ready-to-paste prompt.
• Export fix — private collections now return data to authenticated owners instead of hard-rejecting with 404.
• API key config — keyExpiration.minExpiresIn: 0 allows short-lived tokens; rate limiting left disabled for local dev.
• Vite HMR fix — aligned websocket port in server.ts (was 24678) with the Docker-exposed port (24688).