perf: round 4 — one-pass row paths, drive-selector cache, CalDAV single-parse, streamed Azure, batched hydration

Nine benchmark-gated changes (benches/ROUND4.md; every one ships with a
BEFORE/AFTER bench + equivalence gate, rollback rule as ROUND2/3):

- Row→entity path build: one-pass StoragePath::from_folder_and_name /
  from_joined + normalize_storage_name_owned + alloc-free Display —
  743→417 ns/file-row (1.78x), −5 allocs/row on every listing surface.
- WebDAV drive-selector: per-user readable_cache (single-flight, 30 s
  TTL, explicit invalidation incl. membership + group changes) replaces
  the grants join per request — 441 µs → 0.8 µs (~550x), 0 queries warm.
- CalDAV from_ical/update_ical_data: 8 full IcalParser runs per VEVENT
  → 1 (7.1x per PUT, 4.4x on 50-event imports); alloc-free split_vevents,
  chunk scan without the whole-body uppercase copy (1.4x), borrowed-key
  UID grouping (1.3x), REPORT props no longer cloned.
- PROPFIND emit: partition Vecs dropped (single-pass 404 list) + stack
  rendered RFC 3339/2822 dates, sizes, quoted etags (common::fmt,
  chrono-byte-identical, sweep-tested) on both DAV surfaces — 1.22x
  per page, 17.9→12.0 allocs/row.
- Grant-listing hydration: calendars/address books/playlists batch
  hydrate via = ANY($1) — 15 serial queries → 1 (~13x per sync poll).
- user-flags cache: get→insert → try_get_with single-flight (32→1
  queries per cold herd).
- Azure downloads: whole-blob Vec buffering → streamed SDK pages —
  TTFB 349→4 ms (87x), peak heap 480→1.9 MiB (254x) on 256 MiB blobs;
  new OXICLOUD_AZURE_ENDPOINT_URL override (Azurite/bench hook).
- Face indexing: unbounded per-image tokio::spawn → core-count
  semaphore, permit before blob read — peak heap 1175→176 MiB (6.7x).

Checks: cargo fmt, clippy --all-features --all-targets -D warnings,
cargo test --workspace (523 passed) + --features test_utils. hurl API
suite and dockerized integration DB not runnable in this environment —
left to CI.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017aJu9ghvuT8WqC31ZEGTBA

src/application/services/music_service.rs

@@ -196,15 +196,18 @@ impl MusicUseCase for MusicService {
         // only. Owner is a grant like any other in `role_grants`, so we
         // filter the aggregated set against the owner_id stamped on
         // each row after hydration — cheaper than a second SQL round-trip.
-        let mut playlists: Vec<PlaylistDto> = Vec::with_capacity(playlist_ids.len());
+        // Hydrate in ONE `= ANY` round-trip (was one point SELECT per
+        // accessible playlist). Missing rows (deleted race) drop out of
+        // the result set silently, as before.
         let user_str = user_id.to_string();
-        for id in playlist_ids.drain() {
-            if let Ok(Some(p)) = self.storage.get_playlist(&id.to_string()).await
-                && (include_shared || p.owner_id == user_str)
-            {
-                playlists.push(p);
-            }
-        }
+        let ids: Vec<Uuid> = playlist_ids.drain().collect();
+        let mut playlists: Vec<PlaylistDto> = self
+            .storage
+            .get_playlists_by_ids(&ids)
+            .await?
+            .into_iter()
+            .filter(|p| include_shared || p.owner_id == user_str)
+            .collect();
 
         if include_public {
             let public = self.storage.list_public_playlists(limit, offset).await?;