Button consistency sweep + mobile responsiveness patches

- Standardize modal dismiss/cancel buttons to btn-outline-secondary across 70+ views
- Remove btn-sm from page-level Create and Back buttons (Index + Detail pages)
- Fix Edit buttons on Details pages: btn-secondary -> btn-warning
- Fix form Cancel/Back links: btn-secondary -> btn-outline-secondary
- Add 10 CSS patches to site.css for mobile/tablet responsiveness:
  top-navbar overflow prevention, page-header flex-wrap at 575px,
  table action button min-height override, notification dropdown width cap,
  tablet content padding

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Views/PlatformNotifications/Details.cshtml

@@ -9,7 +9,7 @@
 
 <div class="container-fluid py-3" style="max-width:800px">
     <div class="d-flex align-items-center gap-3 mb-3">
-        <a asp-action="Index" class="btn btn-outline-secondary btn-sm">
+        <a asp-action="Index" class="btn btn-outline-secondary">
             <i class="bi bi-arrow-left me-1"></i>Back
         </a>
         <h4 class="mb-0"><i class="bi bi-bell me-2 text-primary"></i>Notification Details</h4>