perf: keyset/LATERAL SQL shapes, auth+blob-cache single-flight, spool buffers, DTO interning

Round 3 of benchmark-gated optimizations (benches/ROUND3.md; every change
gated by a before/after benchmark — an AFTER that did not beat its BEFORE
was to be rolled back; none needed it. Equivalence gates assert identical
row sequences / byte-identical output on every behavior-preserving rewrite):

DB hot paths (local PG16, EXPLAIN-verified):
- Web-UI listing (list_resources_paged): cursor pushed INSIDE the
  folders/files UNION-ALL branches as sargable row-value comparisons with
  per-branch ORDER/LIMIT + two partial expression indexes
  (folder_id, LOWER(name), id). 20k-entry folder: 26.6 -> 1.3 ms/page
  (19.5x); other sort modes at parity or better. New migration
  20260918000000. [benches/LISTING-KEYSET.md section in ROUND3]
- Photos timeline (list_media_files): per-drive CROSS JOIN LATERAL top-N
  on the timeline index, joins moved above the top-N. 50k-photo library:
  97.4 -> 1.6 ms/page (55.7x). The old "LIMIT stops the scan early"
  comment was refuted by EXPLAIN.
- PROPFIND sub-folders (both DAV surfaces): keyset list_folders_batch off
  idx_folders_unique_name replaces COUNT(*) OVER() + LIMIT/OFFSET
  (5k dirs: 79.7 -> 17.9 ms full walk, 4.5x).

Concurrency:
- Basic-auth cache single-flight (moka try_get_with): 8 concurrent DAV
  connections at TTL expiry paid 8 Argon2id runs (2.6 s CPU + 8x64 MiB);
  now 1 (300 ms). Failed verifications remain uncached.
- CachedBlobBackend per-hash single-flight + unique tmp names: 16
  concurrent cold readers = 16 full remote downloads racing truncating
  writes on ONE deterministic .tmp (corruptible cache); now 1 download
  (16x less egress, 2.8x wall on a shared link) and torn files can never
  be renamed into the cache.

I/O and allocations:
- Chunk-assembly reads 64K -> 512K buffers (2.3x, 8x fewer syscalls);
  chunk-spool writes via BufWriter 512K (5.6x, 32x fewer syscalls).
- S3/Azure put_blob_from_bytes_unsynced overrides: dedup settle no longer
  pays a HEAD probe per new chunk (2 RTT -> 1, 1.8x); Azure stops copying
  every chunk (Bytes -> Body, -0.44 ms - 4 MiB alloc per 4 MiB chunk).
- Entity->DTO mapping: Arc<str> interning of closed-set display fields +
  common MIMEs, 1-alloc etag/size formatting, FolderDto moves instead of
  clones. File row: 11 -> 4 allocs; folder row: 11.8 -> 1 (2.1x faster).
- CardDAV REPORT: deleted dead per-contact vCard pre-generation and the
  O(N^2) uid scan whose result was discarded (5k contacts: 55.7 -> 5.7 ms,
  9.8x); byte-identical XML asserted.
- Search-results cache: byte weigher + 32 MiB budget
  (OXICLOUD_SEARCH_CACHE_MAX_BYTES) replaces the 1000-ENTRY cap that let
  ~300 MiB of enriched rows sit in RSS; read latency parity.
- Dropped aws-config + aws-smithy-types (zero references; -82 dep-graph
  nodes, three SDK stacks gone from every build). tokio "process" is now
  an explicit feature (was enabled transitively by aws-config).

Frontend:
- Cached Intl.DateTimeFormat keyed by (locale, options) in formatDate and
  4 sibling callsites: 20k dates 2612 -> 51 ms (51.6x); vitest gate
  asserts output identity across locales and a 3x floor.

Validation: cargo fmt + clippy --all-features --all-targets -D warnings
clean; 518 unit + 548 integration-cfg tests green; new-shape endpoints
smoke-tested end-to-end over HTTP (all 5 listing sort modes with cursor
walks, WebDAV PROPFIND Depth-1, photos timeline, Basic-auth DAV login);
frontend npm run check clean, new vitest gates green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EBsU2qEzny3A8WQUEuMNCr

src/interfaces/api/handlers/webdav_handler.rs

@@ -781,25 +781,25 @@ async fn build_streaming_propfind_response(
 
         // ── Children (only if Depth == 1) ────────────────────────
         if depth == "1" {
-            let pagination = crate::application::dtos::pagination::PaginationRequestDto {
-                page: 0,
-                page_size: PROPFIND_BATCH_SIZE as usize,
-            };
             let fid_ref = folder_id.as_deref();
 
-            // Stream sub-folders in pages (user-scoped)
-            let mut page = 0usize;
+            // Stream sub-folders in pages (user-scoped, keyset cursor —
+            // O(page) per page off idx_folders_unique_name instead of the
+            // quadratic COUNT(*) OVER() + LIMIT/OFFSET walk; 4.5x on a
+            // 5k-dir parent, benches/FOLDER-KEYSET.md).
+            let mut after_folder: Option<String> = None;
             loop {
-                let pag = crate::application::dtos::pagination::PaginationRequestDto {
-                    page,
-                    page_size: pagination.page_size,
-                };
-                let result = folder_service
-                    .list_folders_paginated_with_perms(fid_ref, user_id, &pag)
+                let batch = folder_service
+                    .list_folders_batch_with_perms(
+                        fid_ref,
+                        user_id,
+                        after_folder.as_deref(),
+                        PROPFIND_BATCH_SIZE as usize,
+                    )
                     .await
                     .map_err(|e| std::io::Error::other(e.to_string()))?;
 
-                if result.items.is_empty() {
+                if batch.is_empty() {
                     break;
                 }
 
@@ -808,25 +808,25 @@ async fn build_streaming_propfind_response(
                 // 1-4.5 s of pure DB chatter on a 2000-child folder
                 // (measured in benches/DEAD-PROPS.md).
                 let subfolder_deads =
-                    folders_dead_props_map(&dead_props_store, &result.items).await;
+                    folders_dead_props_map(&dead_props_store, &batch).await;
 
-                let mut chunk = Vec::with_capacity(result.items.len() * 800);
+                let mut chunk = Vec::with_capacity(batch.len() * 800);
                 {
                     let mut w = Writer::new(&mut chunk);
-                    for subfolder in result.items.iter() {
+                    for subfolder in batch.iter() {
                         let child_dead = dead_props_for(&subfolder.id, &subfolder_deads);
                         let href = format!("{}{}/", base_href, encode_path_segment(&subfolder.name));
                         WebDavAdapter::write_folder_entry_with_dead_props(&mut w, subfolder, &propfind_request, &href, child_dead, quota)
                             .map_err(|e| std::io::Error::other(e.to_string()))?;
                     }
                 }
-                let has_more = result.pagination.has_next;
+                let has_more = (batch.len() as i64) == PROPFIND_BATCH_SIZE;
+                after_folder = batch.last().map(|f| f.name.clone());
                 yield Bytes::from(chunk);
 
                 if !has_more {
                     break;
                 }
-                page += 1;
             }
 
             // Stream files in pages (user-scoped, keyset cursor — O(page)