[tkohr]

PR is based on #220 and its underlying backend PRs.

Changes

• List all configured source databases with their mode (Copy / Direct access).
  • Long names are truncated, with the full name in a tooltip
  • Clicking a row selects the database and shows the schema/table inputs; clicking the selected database goes back to the list
• Show an when no database is configured
• Always offer the database source in the wizard, and drop the database_source feature flag in the backend

Not included yet

• Fixed schema per database: a schema configured on a database isn't preselected and locked yet; that needs a backend config field first
• Non-admin users: GET /source-databases/ is admin-only, so they see the empty state

Note: Code mostly generated with Claude.