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/FixedAssets/Create.cshtml

@@ -7,7 +7,7 @@
     <div class="col-lg-8">
 
         <div class="mb-4">
-            <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 to Asset Register
             </a>
         </div>

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

@@ -14,7 +14,7 @@
 }
 
 <div class="d-flex justify-content-between align-items-center mb-4">
-    <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>Asset Register
     </a>
     <div class="d-flex gap-2">

src/PowderCoating.Web/Views/FixedAssets/Edit.cshtml

@@ -9,7 +9,7 @@
     <div class="col-lg-8">
 
         <div class="mb-4">
-            <a asp-action="Details" asp-route-id="@Model.Id" class="btn btn-outline-secondary btn-sm">
+            <a asp-action="Details" asp-route-id="@Model.Id" class="btn btn-outline-secondary">
                 <i class="bi bi-arrow-left me-1"></i>Back to Asset
             </a>
         </div>