Show schema on UI (Web)

[ka8725]

Implement UI (web version) of the schema diff. It can also show all lines of the schema on UI and the corresponding migration that introduced the change.

See the /rails/migrations route that already has UI for all migrations. Just add a nested page for this with a button "View schema" that leads to it from the entry-point page - /rails/migrations.

As a schema can be very long, add a filter that shows only specific table(s). Avoid any third-party dependencies to implement the search.