refactor(css): maximize usage of variables (1st part, to simplify CSS & style)

note: there is still work to do, but has there are risks to conflict I prefer to commit this first part now

static/css/base/forms.css

@@ -6,14 +6,14 @@
     display: block;
     margin-bottom: 8px;
     font-weight: 500;
-    color: #4a5568;
+    color: var(--color-text-secondary);
 }
 
 .form-group input,
 .form-group textarea {
     width: 100%;
     padding: 10px;
-    border: 1px solid #e2e8f0;
+    border: 1px solid var(--color-border);
     border-radius: 6px;
     font-size: 14px;
 }
@@ -33,28 +33,28 @@
 }
 
 .primary {
-    background-color: #ff5e3a;
-    color: white;
+    background-color: var(--color-accent);
+    color: var(--color-danger-text);
 }
 
 .primary:hover {
-    background-color: #e64a29;
+    background-color: var(--color-accent-hover);
 }
 
 .secondary {
-    background-color: #e2e8f0;
-    color: #4a5568;
+    background-color: var(--color-border);
+    color: var(--color-text-secondary);
 }
 
 .secondary:hover {
-    background-color: #cbd5e0;
+    background-color: var(--color-border-medium);
 }
 
 .danger {
-    background-color: #f56565;
-    color: white;
+    background-color: var( --color-danger-bg);
+    color: var( --color-danger-text);
 }
 
 .danger:hover {
-    background-color: #e53e3e;
+    background-color: var( --color-danger-hover);
 }