feat: implement export functionality for projects and scenarios with CSV and Excel support

static/css/imports.css

@@ -0,0 +1,86 @@
+.import-upload {
+  background-color: var(--surface-color);
+  border: 1px dashed var(--border-color);
+  border-radius: var(--radius-md);
+  padding: 1.5rem;
+  margin-bottom: 1.5rem;
+}
+
+.import-upload__header {
+  margin-bottom: 1rem;
+}
+
+.import-upload__dropzone {
+  border: 2px dashed var(--border-color);
+  border-radius: var(--radius-sm);
+  padding: 2rem;
+  text-align: center;
+  transition: border-color 0.2s ease, background-color 0.2s ease;
+}
+
+.import-upload__dropzone.dragover {
+  border-color: var(--primary-color);
+  background-color: rgba(0, 123, 255, 0.05);
+}
+
+.import-upload__actions {
+  display: flex;
+  gap: 0.75rem;
+  margin-top: 1rem;
+}
+
+.table-cell-actions {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+}
+
+.btn-ghost {
+  background: transparent;
+  border: none;
+  cursor: pointer;
+  padding: 0.25rem 0.5rem;
+  color: var(--text-muted);
+}
+
+.btn-ghost:hover {
+  color: var(--primary-color);
+}
+
+.toast {
+  position: fixed;
+  right: 1rem;
+  bottom: 1rem;
+  display: flex;
+  align-items: center;
+  gap: 0.75rem;
+  padding: 1rem 1.25rem;
+  border-radius: var(--radius-md);
+  color: #fff;
+  box-shadow: var(--shadow-lg);
+  z-index: 1000;
+}
+
+.toast.hidden {
+  display: none;
+}
+
+.toast--success {
+  background-color: #198754;
+}
+
+.toast--error {
+  background-color: #dc3545;
+}
+
+.toast--info {
+  background-color: #0d6efd;
+}
+
+.toast__close {
+  background: none;
+  border: none;
+  color: inherit;
+  cursor: pointer;
+  font-size: 1.1rem;
+}