perf: round 10 — auth alloc purge, parent-herd batching, query-shape pack, NC 304s

Benchmark-gated (benches/ROUND10.md; every change carries a BEFORE/AFTER
harness with equivalence/safety gates — two designs were rejected or
rewritten by their own benches before adoption):

- Auth hot path: TokenClaims/CurrentUser display fields to Arc<str>, role
  to inline SmolStr end-to-end (Bearer, cookie, Basic-auth cache) — 4→1
  allocs per authenticated request, 3→0 per warm DAV request; JWT
  Encoding/Decoding/Validation built once.
- Cold shared-album herd: leader-inline parent batching in PgAclEngine
  (+ cascade try_get_with single-flight) — 100→2 parent queries per
  100-thumb cold herd, herd wall 1.9x, sequential + warm paths unchanged,
  all ROUND8/9 safety gates plus new herd-equivalence gates.
- Query-shape pack: share download double-fetch 2→1 (2.18x), contact-group
  COUNT(*) 14.9x, save_faces UNNEST 3.9x, playlist reorder UNNEST 63.7x
  (now atomic), search files∥folders join! 1.45x, move drive-lookup join!
  2.14x, trash partial (drive_id, trashed_at) indexes, CalDAV event-gate
  narrow read, favorites/recents binary-decode port, dead count_files
  removed.
- NC surface: preview + avatar honour If-None-Match (e2e: 5 KB and 197 KB
  → 0 bytes per revalidation), avatar WebP→PNG transcode memoised,
  PROPFIND/trashbin integer+date emits on stack formatters, folder-header
  enrichment join!, chunk-PUT retry stat folded into create_new open.
- common::fmt integer rendering rewritten on the std 2-digit LUT after the
  round's own bench caught the div-loop losing to to_string (16.1 ns vs
  22.5; speeds every prior-round call site).
- Micro-pack: WebDAV scope probe borrow-only, ShareService base_url
  snapshot, cookie_secure OnceLock, Arc'd AES-GCM cipher, stack request-id,
  tantivy analyzer clone dropped.
- SPA: search stale-guard + AbortController (10→1 completed round-trips,
  stale-clobber gone), getFolder in-flight dedup, gridColumns matchMedia
  hoist (10k→0 style reads).

Backend: cargo fmt + clippy -D warnings clean, 524 tests green.
Frontend: npm run check clean, 301 vitest green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018DdM7V7M3QPW7HEHg3gLov

src/interfaces/nextcloud/uploads_handler.rs

@@ -325,15 +325,16 @@ async fn handle_put_chunk(
         .map_err(|e| AppError::bad_request(format!("Invalid chunk path: {}", e)))?;
 
     let max_chunk = state.core.config.storage.chunk_max_bytes;
-    // A re-PUT of an existing chunk (client retry) makes the running
-    // session counter stale — drop it so the next gate rebuilds from disk.
-    let overwrite = tokio::fs::metadata(&chunk_path).await.is_ok();
     // No client-side integrity contract on the NC chunked surface — the
     // NC desktop client validates the assembled-file ETag against the
     // server-side `oc:checksums` after MOVE. So we skip per-chunk
     // hashing here (peak heap stays at ~one HTTP frame).
+    //
+    // Retry detection (a re-PUT makes the running session counter stale)
+    // rides on the open itself now — `created_fresh` from the `create_new`
+    // probe replaces the extra per-chunk `stat` this path used to issue.
     let streamed = stream_body_to_path(req.into_body(), &chunk_path, max_chunk, None).await?;
-    if overwrite {
+    if !streamed.created_fresh {
         nc.chunked_uploads
             .forget_session_bytes(&user.username, upload_id);
     } else {