fix(frontend): child row stripes, deleted-child visibility, selection completeness

EntryRow.jsx / ChildRow:
- Index-based light/dark classes (child-entry-row--light/dark) replace
  nth-child rules; parity comes from children.map idx so no sibling —
  including the loading div — can shift the stripe order
- Loading div moved outside .child-entries so it never affects child
  row ordering at all
- Accept deletedUids prop; filter expanded children array before render
  so deleted children disappear immediately without waiting for reload

EntriesView.jsx: thread deletedUids through to EntryRow

App.jsx:
- Add deletedUids state; handleEntryDeleted/handleBulkDeleted populate it
- isRoot/hasChildDelete computed from entries before setEntries (safe in
  StrictMode — no side-effects inside updater functions)
- Child delete triggers loadEntries to refresh stale parent child_count
  and total_artifact_bytes
- handleRowClick ctrl/meta cache-miss branch uses det.summary (not det)
  from fetchEntryDetail; archiveId added to dep array
- handleRowClick dep array includes archiveId

frontend/src/styles.css

@@ -2796,8 +2796,8 @@ body.has-audio-bar { padding-bottom: 56px; }
 }
 .child-entry-row:hover { opacity: 1; }
 .child-entry-row:last-child { border-bottom: none; }
-.child-entry-row:nth-child(odd)  { background: var(--paper-3); }
-.child-entry-row:nth-child(even) { background: #f2ede5; }
+.child-entry-row--light { background: var(--paper-3); }
+.child-entry-row--dark  { background: #f2ede5; }
 .child-entry-row.is-selected {
   background: #eee2d2;
   box-shadow: inset 0 0 0 2px var(--accent);