Operator workspace

Use Kepr 2's hierarchy and focused workflows with Kepr 3's existing data. Approved by June, 2026-09-29. Rollback: 0d03d747c5a2.

1. Persistent sidebar; separate profile and site views on the existing site route. Preserve settings across partial forms, show validation input and save confirmation.
2. Overview with repo visibility, issues, sync attention and backup status; searchable repo selection with one settings form. Preserve all existing actions.
3. Notifications: inspect Kepr 2; confirm delivery scope before adding storage or routes.

Verify each slice with relevant tests and the four repository gates. Use an isolated browser for desktop and phone layouts, sign-in and operator form submissions. No schema changes, new dependencies, or Koh bucket writes for the workspace redesign.