fix(secrets): ship the delete modal's own styles under collision-proof class names (0.2.3)

Fixes scadaproj#2. ConfirmDeleteModal used the bare `modal` class and the
Secrets.Ui RCL shipped no CSS at all, silently depending on the host having
no opinion about that selector. Bootstrap 5 does: `.modal { display: none }`
made the delete modal permanently invisible on every Bootstrap host
(ScadaBridge, OtOpcUa, HistorianGateway — confirmed live on the first two)
while every @onclick handler kept working. Only MxGateway, the lone
Bootstrap-free host, could ever have rendered it.

Fix, entirely inside the RCL so a package bump repairs every host with no
host-side changes:
- class vocabulary renamed to zb-secrets-modal / -backdrop / -card / -title
  so no host framework selector can match the elements;
- the component emits its own <style> block alongside the markup. Scoped
  .razor.css was deliberately NOT used: three of the four family hosts never
  link a scoped-CSS bundle, so isolation CSS would silently fail to load —
  the exact defect class being fixed. Theme tokens with fallbacks keep the
  card legible even on a host without the kit stylesheet.
- data-testids unchanged, so existing Playwright gates and bUnit tests keep
  their selectors.

New bUnit pins: no Bootstrap-reserved class name appears in the rendered
markup, and the component ships a style block that both positions the
overlay and gives it a display mode. Suite 182 pass / 0 fail / 0.2.3.

Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts

ZB.MOM.WW.Secrets/tests/ZB.MOM.WW.Secrets.Ui.Tests/ConfirmDeleteModalTests.cs

@@ -34,7 +34,7 @@ public class ConfirmDeleteModalTests : TestContext
             .Add(c => c.OnDeleted, () => deleted = true));
 
         // The confirmation is a rendered in-page modal element.
-        Assert.NotEmpty(cut.FindAll(".modal"));
+        Assert.NotEmpty(cut.FindAll(".zb-secrets-modal"));
         Assert.Contains("db/primary", cut.Markup);
 
         cut.Find("[data-testid=confirm-delete]").Click();
@@ -133,6 +133,59 @@ public class ConfirmDeleteModalTests : TestContext
             .Add(c => c.Visible, false)
             .Add(c => c.Name, name));
 
-        Assert.Empty(cut.FindAll(".modal"));
+        Assert.Empty(cut.FindAll(".zb-secrets-modal"));
+    }
+
+    /// <summary>
+    ///     scadaproj#2 regression pins. The modal previously used the bare <c>modal</c> class and
+    ///     shipped no CSS, silently depending on the host having no opinion about it — Bootstrap 5's
+    ///     <c>.modal { display: none }</c> made the overlay permanently invisible on every
+    ///     Bootstrap host (ScadaBridge, OtOpcUa, HistorianGateway) while every handler kept working.
+    /// </summary>
+    [Fact]
+    public void ConfirmDeleteModal_UsesNoFrameworkReservedClassNames()
+    {
+        var cut = RenderVisibleModal();
+
+        // Bootstrap owns these selectors; any element carrying one is again at the mercy of
+        // whatever stylesheet the host happens to link.
+        string[] reserved = ["modal", "modal-title", "modal-backdrop", "modal-dialog", "modal-content"];
+        foreach (string cls in reserved)
+        {
+            Assert.Empty(cut.FindAll($".{cls}"));
+        }
+
+        // The elements themselves still render, under the component-scoped vocabulary.
+        Assert.NotEmpty(cut.FindAll(".zb-secrets-modal"));
+        Assert.NotEmpty(cut.FindAll(".zb-secrets-modal-backdrop"));
+        Assert.NotEmpty(cut.FindAll(".zb-secrets-modal-card"));
+    }
+
+    [Fact]
+    public void ConfirmDeleteModal_ShipsItsOwnStyles()
+    {
+        var cut = RenderVisibleModal();
+
+        // The RCL must carry the modal's CSS itself: no family host links a Secrets.Ui
+        // stylesheet, and three of the four never link a scoped-CSS bundle at all — so any
+        // styling delivered outside the component silently fails to load exactly like the
+        // original defect. The inline block must both position the overlay and give it a
+        // display mode, or a host reset/framework rule can hide it again.
+        var style = cut.FindAll("style").SingleOrDefault();
+        Assert.NotNull(style);
+        Assert.Contains(".zb-secrets-modal", style.TextContent);
+        Assert.Contains("position: fixed", style.TextContent);
+        Assert.Contains("display: flex", style.TextContent);
+    }
+
+    private IRenderedComponent<ConfirmDeleteModal> RenderVisibleModal()
+    {
+        Services.AddSingleton<ISecretStore>(new RecordingSecretStore());
+        Services.AddSingleton<IAuditWriter>(new CapturingAuditWriter());
+        this.AddTestAuthorization().SetAuthorized("carol");
+
+        return RenderComponent<ConfirmDeleteModal>(p => p
+            .Add(c => c.Visible, true)
+            .Add(c => c.Name, new SecretName("db/primary")));
     }
 }