Refactor CSS styles and introduce theme variables

- Removed redundant CSS rules and consolidated styles across dashboard, forms, imports, projects, and scenarios.
- Introduced new color variables in theme-default.css for better maintainability and consistency.
- Updated existing styles to utilize new color variables, enhancing the overall design.
- Improved responsiveness and layout of various components, including tables and cards.
- Ensured consistent styling for buttons, links, and headers across the application.

static/css/dashboard.css

@@ -2,17 +2,6 @@
   --dashboard-gap: 1.5rem;
 }
 
-.dashboard-header {
-  align-items: center;
-}
-
-.header-actions {
-  display: flex;
-  gap: 0.75rem;
-  flex-wrap: wrap;
-  justify-content: flex-end;
-}
-
 .dashboard-metrics {
   display: grid;
   gap: var(--dashboard-gap);
@@ -20,36 +9,6 @@
   margin-bottom: 2rem;
 }
 
-.metric-card {
-  background: var(--card);
-  border-radius: var(--radius);
-  padding: 1.5rem;
-  box-shadow: var(--shadow);
-  border: 1px solid var(--color-border);
-  display: flex;
-  flex-direction: column;
-  gap: 0.35rem;
-}
-
-.metric-card h2 {
-  margin: 0;
-  font-size: 1rem;
-  color: var(--muted);
-  text-transform: uppercase;
-  letter-spacing: 0.08em;
-}
-
-.metric-value {
-  font-size: 2rem;
-  font-weight: 700;
-  margin: 0;
-}
-
-.metric-caption {
-  color: var(--color-text-subtle);
-  font-size: 0.85rem;
-}
-
 .dashboard-grid {
   display: grid;
   gap: var(--dashboard-gap);
@@ -67,16 +26,6 @@
   gap: var(--dashboard-gap);
 }
 
-.table-link {
-  color: var(--brand-2);
-  text-decoration: none;
-}
-
-.table-link:hover,
-.table-link:focus {
-  text-decoration: underline;
-}
-
 .timeline {
   list-style: none;
   margin: 0;
@@ -107,7 +56,9 @@
   padding: 0.75rem;
   border-radius: var(--radius-sm);
   background: rgba(209, 75, 75, 0.16);
+  background: color-mix(in srgb, var(--color-danger) 16%, transparent);
   border: 1px solid rgba(209, 75, 75, 0.3);
+  border: 1px solid color-mix(in srgb, var(--color-danger) 30%, transparent);
 }
 
 .links-list a {
@@ -128,23 +79,4 @@
   .grid-sidebar {
     grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
   }
-
-  .header-actions {
-    justify-content: flex-start;
-  }
-}
-
-@media (max-width: 640px) {
-  .metric-card {
-    padding: 1.25rem;
-  }
-
-  .metric-value {
-    font-size: 1.75rem;
-  }
-
-  .header-actions {
-    flex-direction: column;
-    align-items: stretch;
-  }
 }