Require II for public database creation and improve dashboard navigation

[humandebri]

Summary

• Gate public database creation on principal, preventing creation before Internet Identity is connected.
• Update the create button label by connection state, explicitly showing Connect Internet Identity and Connect OISY or Plug.
• Move the create action into the public database area on the home page so unauthenticated users can still find the next step.
• Make the management header logo link back home to provide a clearer return path.
• Update the dashboard check script to match the new labels and layout.

Testing

• Updated expectations in scripts/check-dashboard.mjs.
• Confirmed the static checks for the changed behavior pass.