feat(ui): rewrite frontend in React with Vite

- Scaffold Vite+React project in frontend/ (bun, react 18, @vitejs/plugin-react)
- vite.config.js outputs to crates/archivr-server/static/ directly
- src/utils.js: formatBytes, valueText, formatTimestamp, SOURCE_ICONS, sourceIconSvg
- src/api.js: typed fetch wrappers for all API endpoints
- App.jsx: full state management, archive switching, debounced search,
  tag filter, view routing, capture dialog orchestration
- components/Topbar.jsx: archive switcher, nav, capture button
- components/CaptureDialog.jsx: native <dialog> ref with showModal/close,
  Escape key support, locator validation
- components/EntriesView.jsx + EntryRow.jsx: flex table with source icons,
  type pills, keyboard selection
- components/ContextRail.jsx: parallel detail+tags fetch, stale-race guard
  via selectSeqRef, inline tag assign/remove
- components/RunsView.jsx: runs kept as <table> (matches original)
- components/AdminView.jsx: mounted archives list
- components/TagsView.jsx: recursive tag tree with active state
- Remove old app.js; styles.css moved to frontend/src/ (Vite bundles it)

frontend/src/components/EntryRow.jsx

@@ -0,0 +1,24 @@
+import { formatTimestamp, formatBytes, valueText, sourceIconSvg } from '../utils';
+
+export default function EntryRow({ entry, isSelected, onSelect }) {
+  return (
+    <div
+      className={isSelected ? 'is-selected' : undefined}
+      tabIndex={0}
+      data-entry-uid={entry.entry_uid}
+      onClick={onSelect}
+      onKeyDown={e => { if (e.key === 'Enter') onSelect(); }}
+    >
+      <div className="col-added">{formatTimestamp(entry.archived_at)}</div>
+      <div className="col-title">
+        <span className="source-icon" dangerouslySetInnerHTML={{ __html: sourceIconSvg(entry.source_kind) }} />
+        <span className="entry-title">{valueText(entry.title) || valueText(entry.entry_uid)}</span>
+      </div>
+      <div className="col-type">
+        <span className="type-pill">{valueText(entry.entity_kind)}</span>
+      </div>
+      <div className="col-size">{formatBytes(entry.total_artifact_bytes)}</div>
+      <div className="url-cell col-url">{valueText(entry.original_url)}</div>
+    </div>
+  );
+}