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/PurchaseOrders/Edit.cshtml

@@ -1,4 +1,4 @@
-@using PowderCoating.Application.DTOs.PurchaseOrder
+@using PowderCoating.Application.DTOs.PurchaseOrder
 @model UpdatePurchaseOrderDto
 
 @{
@@ -27,14 +27,14 @@
     </a>
 </div>
 
-<div class="alert alert-info d-flex align-items-center gap-2 mb-3">
+<div class="alert alert-info alert-permanent d-flex align-items-center gap-2 mb-3">
     <i class="bi bi-info-circle-fill"></i>
     <span>Only <strong>Draft</strong> purchase orders can be edited.</span>
 </div>
 
 @if (!ViewData.ModelState.IsValid)
 {
-    <div class="alert alert-danger">
+    <div class="alert alert-danger alert-permanent">
         <ul class="mb-0">
             @foreach (var error in ViewData.ModelState.Values.SelectMany(v => v.Errors))
             {
@@ -57,7 +57,7 @@
                             <label asp-for="VendorId" class="form-label fw-semibold">Vendor <span class="text-danger">*</span></label>
                             <select asp-for="VendorId" asp-items="@ViewBag.Vendors" class="form-select"
                                     data-quick-add-url="/Vendors/Create" data-quick-add-title="Add New Vendor">
-                                <option value="__new__">+ Add New Vendor…</option>
+                                <option value="__new__">+ Add New Vendor…</option>
                             </select>
                             <span asp-validation-for="VendorId" class="text-danger small"></span>
                         </div>
@@ -114,12 +114,12 @@
                         <div class="col-md-6">
                             <label asp-for="Notes" class="form-label fw-semibold">Notes</label>
                             <textarea asp-for="Notes" class="form-control" rows="3"
-                                      placeholder="Visible on PO…"></textarea>
+                                      placeholder="Visible on PO…"></textarea>
                         </div>
                         <div class="col-md-6">
                             <label asp-for="InternalNotes" class="form-label fw-semibold">Internal Notes</label>
                             <textarea asp-for="InternalNotes" class="form-control" rows="3"
-                                      placeholder="Internal use only…"></textarea>
+                                      placeholder="Internal use only…"></textarea>
                         </div>
                     </div>
                 </div>