fix(dashboard): admin-UI cleanup sweep

Family-wide admin-UI cleanup pass (scadaproj admin_ui_cleanup.md) applied to the
Blazor dashboard. Behaviour is unchanged throughout — no @onclick, disabled,
binding, auth gate, or arm->confirm flow was touched.

Uncontrolled error text is now truncated at the render site. Fault messages,
Galaxy load errors, and browse-tree load failures were rendered in full into
fixed-width table cells, where a long exception string blows out the column.
Each site gets DashboardDisplay.Abbreviate plus a title attribute carrying the
untruncated text, so nothing becomes unreachable. Abbreviate is length-checked
rather than a bare range slice: `value[..n]` on a shorter string throws and
takes the whole page render down with it. The two detail views whose entire
purpose is to show one fault in full — SessionDetailsPage and GalaxyPage's
Last Error — are deliberately left untruncated.

Two classes referenced from markup had no definition anywhere in the sheet.
.browse-stale-banner was inert; .tree-load-status was a real visual defect —
loading and failed-to-load rows sit among .tree-row siblings and carry the same
leading .tree-toggle-empty spacer, but that spacer only takes its width as a
flex item, so without a flex container those rows lost their indent.

Confirm/cancel pairs in ConfirmDialog and the API-key create form are now
btn-groups with role="group" and an aria-label, replacing margin-spaced loose
buttons.

Removes a paragraph on GalaxyPage naming internal RPCs (DiscoverHierarchy,
GetLastDeployTime) — implementation detail with no meaning to a dashboard
operator.

Verified in a real browser, not bUnit: full build clean, 879/879 tests, and a
live gate against a running dashboard with a genuine ~250-char SqlClient
exception as the erroring row. Results per check, including the checks that
could NOT be exercised without an x86 worker, are recorded in
docs/plans/2026-08-11-dashboard-ui-sweeps.md.

That plan doc also records a correction: this app is NOT Bootstrap-free. The
sweep brief said it was, citing the scadaproj index; libman.json pins
bootstrap 5.3.3 and App.razor:7 links it ahead of the theme. The stale claim had
already cost this app one skipped family sweep (scadaproj#2, the /admin/secrets
modal), so that modal was live-gated here too and passes.

src/ZB.MOM.WW.MxGateway.Server/Dashboard/Components/Pages/ApiKeysPage.razor

@@ -133,8 +133,10 @@ else
                                         </div>
 
                                         <div class="mt-3">
-                                            <button type="submit" class="btn btn-success btn-sm me-1" disabled="@IsBusy">Save</button>
-                                            <button type="button" class="btn btn-outline-secondary btn-sm" disabled="@IsBusy" @onclick="CloseCreateDialog">Cancel</button>
+                                            <div class="btn-group btn-group-sm" role="group" aria-label="Create API key actions">
+                                                <button type="submit" class="btn btn-success" disabled="@IsBusy">Save</button>
+                                                <button type="button" class="btn btn-outline-secondary" disabled="@IsBusy" @onclick="CloseCreateDialog">Cancel</button>
+                                            </div>
                                         </div>
                                     </div>
                                 </div>