feat(centralui): rebrand web UI to ScadaBridge + technical-light theme

Rename the user-facing product name from ScadaLink to ScadaBridge across
the six display strings (browser title, sidebar brand, login + not-authorized
headings, dashboard welcome/subtitle). Namespaces, assemblies, config keys,
and _content/ScadaLink.CentralUI asset routes are unchanged.

Apply the technical-light design system: vendor theme.css + IBM Plex fonts
into the CentralUI RCL, include theme.css globally (after Bootstrap so its
--bs-* token overrides win), and restyle the layout chrome to a light
sidebar — white surface, hairline rules, ink text, accent-blue active item,
the brand accent mark. Page markup stays Bootstrap and inherits the warm
paper background, Plex type, accent, and hairline borders via the tokens.

Tests: build 0 warnings; bUnit 542 passed; Playwright 64 passed.

src/ScadaLink.CentralUI/Components/Layout/MainLayout.razor

@@ -17,7 +17,7 @@
         <NavMenu />
     </div>
 
-    <main class="flex-grow-1 p-3" style="background-color: #f8f9fa;">
+    <main class="flex-grow-1 p-3">
         @Body
     </main>
 </div>