[tkohr]

PR adds the first frontend part for the direct access DBs. It is stacked on the admin_table_per_schema_list branch of the last of the three corresponding backend PRs. The functionality only covers the first of these PRs so far.

Changes

• Move the schema and table inputs into a new app-data-source-db component
• Show the selected source database in a box with its access type (Copy / Direct access).
• For direct access databases:
  • Ask for the title in step 1; it is cleared when the schema or table changes
  • Enable the table input once a schema is set, and the title input once schema and table are set
  • Show a dedicated "Create the dataset" button, enabled once schema, table and title are set
• Add a SourceDatabaseStore (GET /source-databases/); the selected database key is passed on in the source data (dbKey)

Not included yet

• Database picker: the first database is preselected; the picker comes in a separate PR
• Creating a direct access dataset: the button doesn't submit yet; that needs a new backend endpoint
• Non-admin users: GET /source-databases/ is admin-only, so they see no database box and go through the copy flow
• Schema and table: still free text inputs

Note: Code has mainly been generated via Claude.