Design consistency audit fixes: alerts, cards, dark mode, utilities

Alert sweep (113 alerts, 79 files):
  All persistent static banners now carry alert-permanent so the
  layout's 5-second auto-dismiss cannot swallow guidance, warnings,
  or validation errors. Transient dismissible toasts left untouched.

CSS fixes (site.css):
  .card.shadow-sm      — strips rogue border from ~40 drifted cards
  .card-header.bg-white — rebinds to var(--bs-body-bg) so card
                          headers follow dark/light theme correctly
  Typography utilities  — .text-2xs (.68rem), .text-xs (.73rem)
  Token color classes   — .text-ember, .text-ok, .text-bad,
                          .text-warn, .text-cool, .bg-paper-2
  Layout utilities      — .mw-xs/sm/md/lg replace inline max-width
  Comment              — documents text-ember vs text-primary intent

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

src/PowderCoating.Web/Views/Expenses/Index.cshtml

@@ -1,4 +1,4 @@
-@model List<PowderCoating.Application.DTOs.Accounting.ExpenseListDto>
+@model List<PowderCoating.Application.DTOs.Accounting.ExpenseListDto>
 
 @{
     ViewData["Title"] = "Expenses";
@@ -23,7 +23,7 @@
 
 @if ((decimal)ViewBag.TotalAmount > 0)
 {
-    <div class="alert alert-info d-flex align-items-center gap-2 mb-4">
+    <div class="alert alert-info alert-permanent d-flex align-items-center gap-2 mb-4">
         <i class="bi bi-info-circle fs-5"></i>
         <span>Total shown: <strong>@(((decimal)ViewBag.TotalAmount).ToString("C"))</strong></span>
     </div>
@@ -34,7 +34,7 @@
         <form method="get" class="row g-2 align-items-end">
             <div class="col-md-3">
                 <input type="search" name="search" value="@ViewBag.Search" class="form-control"
-                       placeholder="Search memo or vendor…" />
+                       placeholder="Search memo or vendor…" />
             </div>
             <div class="col-md-3">
                 <select name="accountId" class="form-select">