ApplicationDbContext: drop redundant HasOne on 3 Client navs

LoadClientAsync(id) on ClientController used to trip an
IndexOutOfRangeException at the InMemory shaper for any
.Include() of one of three Client navs: RedirectUris,
AllowedScopes, AllowedGrantTypes. Five other Client navs (with
the same EF shape and the same application-level config) worked
fine.

Bisection pointed at the InMemory provider; that hypothesis was
wrong. The real cause is in ApplicationDbContext.OnModelCreating:
yavsc was redeclaring the HasOne<Client>().WithMany(...).
HasForeignKey(e => e.ClientId) for all eight Client* navs. The
same relation is already declared (more completely, with
.IsRequired().OnDelete(DeleteBehavior.Cascade)) by
IdentityServer8's ConfigureClientStore via ModelBuilderExtensions.

The redundant mapping on three specific entities — ClientScope,
ClientRedirectUri, ClientGrantType — interacts with the InMemory
provider's shaper in a way that throws IndexOutOfRange. Removing
the redundancy fixes it.

This commit also walks back b12c272d:
- Drops .AsSplitQuery() from LoadClientAsync (no longer needed
  for the InMemory shaper, and the Postgres path it was a hedge
  against was a false alarm — there is no Postgres production
  bug here, only an InMemory shaper quirk surfaced by the
  redundant mapping).
- Removes the 9 Bisect_*_alone tests that were the artefact of
  the provider-hypothesis phase. They pointed at the right
  entities but for the wrong reason.
- Keeps EditRedirectUris_GET_after_add_lists_both_uris as the
  end-to-end regression sentinel: with the fix in place, it
  loads a Client with two RedirectUris and asserts both are
  rendered. Without the fix, it fails with IndexOutOfRange.

src/Yavsc.Org/Controllers/Administration/ClientController.Collections.cs

@@ -287,7 +287,6 @@ public partial class ClientController
 
     private async Task<Client?> LoadClientAsync(int id)
         => await dbContext.Clients
-            .AsSplitQuery()
             .Include(c => c.RedirectUris)
             .Include(c => c.PostLogoutRedirectUris)
             .Include(c => c.AllowedScopes)