Add frontend components for project/package/tag hierarchy views

- Create reusable UI components: Badge, Breadcrumb, Card, DataTable,
  FilterChip, Pagination, SearchInput, SortDropdown
- Update Home page with search, sort, filter, and pagination
- Update ProjectPage with package stats, format filtering, keyboard nav
- Update PackagePage with DataTable for tags, copy artifact ID, metadata
- Add TypeScript types for paginated responses and list params
- Update API client with pagination and filter query param support
- URL-based state persistence for all filter/sort/page params
- Keyboard navigation (Backspace to go up hierarchy)

frontend/src/components/SortDropdown.css

@@ -0,0 +1,95 @@
+/* SortDropdown Component */
+.sort-dropdown {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  position: relative;
+}
+
+.sort-dropdown__trigger {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 8px 12px;
+  background: var(--bg-tertiary);
+  border: 1px solid var(--border-primary);
+  border-radius: var(--radius-md);
+  font-size: 0.8125rem;
+  color: var(--text-secondary);
+  cursor: pointer;
+  transition: all var(--transition-fast);
+}
+
+.sort-dropdown__trigger:hover {
+  background: var(--bg-hover);
+  color: var(--text-primary);
+  border-color: var(--border-secondary);
+}
+
+.sort-dropdown__chevron {
+  transition: transform var(--transition-fast);
+}
+
+.sort-dropdown__chevron--open {
+  transform: rotate(180deg);
+}
+
+.sort-dropdown__order {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 32px;
+  height: 32px;
+  padding: 0;
+  background: var(--bg-tertiary);
+  border: 1px solid var(--border-primary);
+  border-radius: var(--radius-md);
+  color: var(--text-secondary);
+  cursor: pointer;
+  transition: all var(--transition-fast);
+}
+
+.sort-dropdown__order:hover {
+  background: var(--bg-hover);
+  color: var(--text-primary);
+  border-color: var(--border-secondary);
+}
+
+.sort-dropdown__menu {
+  position: absolute;
+  top: 100%;
+  left: 0;
+  margin-top: 4px;
+  min-width: 180px;
+  background: var(--bg-secondary);
+  border: 1px solid var(--border-primary);
+  border-radius: var(--radius-md);
+  box-shadow: var(--shadow-lg);
+  z-index: 100;
+  overflow: hidden;
+}
+
+.sort-dropdown__option {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  width: 100%;
+  padding: 10px 14px;
+  background: transparent;
+  border: none;
+  font-size: 0.8125rem;
+  color: var(--text-secondary);
+  cursor: pointer;
+  transition: all var(--transition-fast);
+  text-align: left;
+}
+
+.sort-dropdown__option:hover {
+  background: var(--bg-hover);
+  color: var(--text-primary);
+}
+
+.sort-dropdown__option--selected {
+  color: var(--accent-primary);
+  font-weight: 500;
+}