style: Update UI with warmer, softer color palette

Replace default Bootstrap grays with warm off-whites and subtle borders.
Adds consistent styling for cards, forms, headings, and tables.

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

CutList.Web/wwwroot/css/app.css

@@ -1,5 +1,7 @@
 html, body {
     font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
+    color: #333;
+    background-color: #f8f7f5;
 }
 
 h1:focus {
@@ -77,6 +79,8 @@ a, .btn-link {
 
 main {
     flex: 1;
+    background-color: #f8f7f5;
+    box-shadow: inset 4px 0 8px -4px rgba(0, 0, 0, 0.08);
 }
 
 .sidebar {
@@ -84,8 +88,8 @@ main {
 }
 
 .top-row {
-    background-color: #f7f7f7;
-    border-bottom: 1px solid #d6d5d5;
+    background-color: #f3f1ee;
+    border-bottom: 1px solid #e0ddd8;
     justify-content: flex-end;
     height: 3.5rem;
     display: flex;
@@ -158,20 +162,60 @@ main {
 }
 
 /* Card improvements */
+.card {
+    background-color: #fdfcfb;
+    border-color: #e0ddd8;
+}
+
 .card-header {
-    background-color: #f8f9fa;
+    background-color: #f0eeeb;
+    border-bottom-color: #e0ddd8;
 }
 
 /* Form improvements */
 .form-label {
     font-weight: 500;
     margin-bottom: 0.25rem;
+    color: #444;
 }
 
 .form-text {
     font-size: 0.8rem;
 }
 
+.form-control, .form-select {
+    background-color: #fdfcfb;
+    border-color: #d5d0ca;
+    color: #333;
+}
+
+.form-control:focus, .form-select:focus {
+    background-color: #fff;
+    border-color: #258cfb;
+}
+
+.form-control::placeholder {
+    color: #aaa;
+}
+
+/* Soften headings */
+h1, h2, h3, h4, h5, h6 {
+    color: #2a2a2a;
+}
+
+h1 {
+    font-weight: 600;
+}
+
+/* Table softening */
+.table {
+    color: #333;
+}
+
+.table > :not(caption) > * > * {
+    background-color: transparent;
+}
+
 /* Better mobile responsiveness for tables */
 @media (max-width: 768px) {
     .table-responsive-stack td,