Add DAST, graph modules, toast notifications, and dashboard enhancements

Add DAST scanning and code knowledge graph features across the stack:
- compliance-dast and compliance-graph workspace crates
- Agent API handlers and routes for DAST targets/scans and graph builds
- Core models and traits for DAST and graph domains
- Dashboard pages for DAST targets/findings/overview and graph explorer/impact
- Toast notification system with auto-dismiss for async action feedback
- Button click animations and disabled states for better UX

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

compliance-dashboard/assets/main.css

@@ -300,6 +300,87 @@ tr:hover {
     color: var(--text-secondary);
 }
 
+/* Toast notifications */
+.toast-container {
+    position: fixed;
+    top: 20px;
+    right: 20px;
+    z-index: 50;
+    display: flex;
+    flex-direction: column;
+    gap: 8px;
+    pointer-events: none;
+}
+
+.toast {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    gap: 12px;
+    min-width: 280px;
+    max-width: 420px;
+    padding: 12px 16px;
+    border-radius: 8px;
+    font-size: 14px;
+    font-weight: 500;
+    pointer-events: auto;
+    animation: toast-in 0.3s ease-out;
+}
+
+.toast-success {
+    background: rgba(34, 197, 94, 0.15);
+    border: 1px solid var(--success);
+    color: #86efac;
+}
+
+.toast-error {
+    background: rgba(239, 68, 68, 0.15);
+    border: 1px solid var(--danger);
+    color: #fca5a5;
+}
+
+.toast-info {
+    background: rgba(59, 130, 246, 0.15);
+    border: 1px solid var(--info);
+    color: #93c5fd;
+}
+
+.toast-dismiss {
+    background: none;
+    border: none;
+    color: inherit;
+    font-size: 18px;
+    cursor: pointer;
+    opacity: 0.7;
+    padding: 0 4px;
+    line-height: 1;
+}
+
+.toast-dismiss:hover {
+    opacity: 1;
+}
+
+@keyframes toast-in {
+    from {
+        transform: translateX(100%);
+        opacity: 0;
+    }
+    to {
+        transform: translateX(0);
+        opacity: 1;
+    }
+}
+
+/* Button click animation + disabled */
+.btn:active {
+    transform: scale(0.95);
+}
+
+.btn:disabled {
+    opacity: 0.6;
+    cursor: not-allowed;
+}
+
 @media (max-width: 768px) {
     .sidebar {
         transform: translateX(-100%);