WEB-669 fix: Replace hardcoded colors with CSS variables for dark mode support

src/app/shared/tabs/entity-notes-tab/entity-notes-tab.component.scss

@@ -17,7 +17,7 @@
 
 .tab-container h3 {
   margin-bottom: 20px;
-  color: #333;
+  color: var(--md-sys-color-on-surface, #333);
   font-weight: 500;
 }
 
@@ -51,8 +51,8 @@
 }
 
 .note-card {
-  background: white;
-  border: 1px solid #e0e0e0;
+  background: var(--md-sys-color-surface, white);
+  border: 1px solid var(--md-sys-color-on-surface-variant, #e0e0e0);
   border-radius: 0.2rem;
   padding: 1rem;
   margin-bottom: 1rem;
@@ -62,11 +62,11 @@
 
 .note-card:hover {
   box-shadow: 0 4px 8px rgb(0 0 0 / 12%);
-  border-color: #d0d0d0;
+  border-color: var(--md-sys-color-on-surface-variant, #d0d0d0);
 }
 
 .note-content {
-  color: #333;
+  color: var(--md-sys-color-on-surface, #333);
   font-size: 14px;
   line-height: 1rem;
   margin: 0;
@@ -83,22 +83,22 @@
   justify-content: space-between;
   align-items: center;
   padding-top: 0.65rem;
-  border-top: 1px solid #f0f0f0;
+  border-top: 1px solid var(--md-sys-color-on-surface-variant, #f0f0f0);
 }
 
 .note-meta {
-  color: #666;
+  color: var(--md-sys-color-on-surface-variant, #666);
   font-size: 12px;
 }
 
 .created-by {
   font-weight: 500;
-  color: #007acc;
+  color: var(--md-sys-color-primary, #007acc);
   margin-bottom: 2px;
 }
 
 .created-date {
-  color: #888;
+  color: var(--md-sys-color-on-surface-variant, #888);
 }
 
 .note-actions {
@@ -115,11 +115,11 @@
 .empty-state {
   text-align: center;
   padding: 40px 20px;
-  color: #666;
+  color: var(--md-sys-color-on-surface-variant, #666);
   font-style: italic;
-  background: #fafafa;
+  background: var(--md-sys-color-surface-container-low, #fafafa);
   border-radius: 8px;
-  border: 1px dashed #ddd;
+  border: 1px dashed var(--md-sys-color-on-surface-variant, #ddd);
 }
 
 .m-r-10 {