refactor(theme): unify components into ZB.MOM.WW.Theme namespace

Add @namespace ZB.MOM.WW.Theme to each component .razor file so the
Razor compiler places all four components in the flat ZB.MOM.WW.Theme
namespace rather than ZB.MOM.WW.Theme.Components. Remove the now-
redundant global using ZB.MOM.WW.Theme.Components from both _Imports
files. Also add @namespace ZB.MOM.WW.Theme to the root _Imports.razor.
Consumers need only @using ZB.MOM.WW.Theme. All 14 tests green.

ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/BrandBar.razor

@@ -1,4 +1,5 @@
 @* Components/BrandBar.razor *@
+@namespace ZB.MOM.WW.Theme
 <div class="brand">
     @if (Logo is not null) { @Logo }
     else { <span class="mark">&#9646;</span> }

ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailItem.razor

@@ -1,4 +1,5 @@
 @* Components/NavRailItem.razor *@
+@namespace ZB.MOM.WW.Theme
 <NavLink class="rail-link" href="@Href" Match="@Match" ActiveClass="active">
     @if (Icon is not null) { <span class="rail-ico">@Icon</span> }
     @Text

ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailSection.razor

@@ -1,5 +1,6 @@
 @* Components/NavRailSection.razor — CSS-only collapsible (no JS, works in static SSR).
    Apps that want cookie-persisted expand state keep their own interactive NavSection. *@
+@namespace ZB.MOM.WW.Theme
 <details class="rail-section" open="@Expanded">
     <summary class="rail-eyebrow-toggle"><span class="rail-eyebrow-label">@Title</span></summary>
     <div class="rail-section-body">@ChildContent</div>

ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/StatusPill.razor

@@ -1,4 +1,5 @@
 @* Components/StatusPill.razor *@
+@namespace ZB.MOM.WW.Theme
 <span class="chip @ChipClass">@ChildContent</span>
 
 @code {

ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/_Imports.razor

@@ -1,5 +1,5 @@
+@namespace ZB.MOM.WW.Theme
 @using Microsoft.AspNetCore.Components
 @using Microsoft.AspNetCore.Components.Routing
 @using Microsoft.AspNetCore.Components.Web
 @using ZB.MOM.WW.Theme
-@using ZB.MOM.WW.Theme.Components

ZB.MOM.WW.Theme/tests/ZB.MOM.WW.Theme.Tests/_Imports.cs

@@ -2,4 +2,3 @@ global using Bunit;
 global using Xunit;
 global using Microsoft.AspNetCore.Components;
 global using ZB.MOM.WW.Theme;
-global using ZB.MOM.WW.Theme.Components;