perf: serve ranges from RAM cache, stream ZIPs, overlap ingest settle, O(1) chunk gate

Round 2 of benchmark-gated optimizations (benches/ROUND2.md; every change
gated by a before/after in examples/bench_round2.rs — an AFTER that did
not beat its BEFORE was to be rolled back; none needed it):

- Range requests (REST/DAV/shares) answered from the moka content cache
  for sub-10MB files: PG resolve + open/seek/read -> Bytes::slice.
  256KiB seeks: 1,730/s -> 3.7M/s (p50 552us -> 0.15us).
- Streaming folder/share ZIPs via tokio duplex: TTFB no longer scales
  with archive size (326ms -> 0.4ms on 192MiB corpus; total also faster).
  Content-Length dropped (size unknown up front).
- NC chunked-upload per-PUT gate: O(k) directory scan+stat -> in-RAM
  per-session counter (lazy rebuild on cold start). 1,000-chunk upload
  gate cost: 33.1s -> 0.09s cumulative.
- Delta download + commit-verify now use the CDC path's
  buffered(read_prefetch) read-ahead: 64-chunk drain at 5ms open
  latency 440ms -> 51ms; order preserved.
- CDC ingest settles batches on a spawned task (depth-1 pipeline) so
  the source stream keeps flowing during PG pin + backend writes;
  rollback ledger shared + lock-serialized so compensation stays exact
  on cancellation. 512MiB paced ingest: 60-69 -> 74-75 MB/s.
  OXICLOUD_INGEST_OVERLAP=0 restores inline settling (ops/bench hatch).
- Frontend: instant-upload BLAKE3 hashing moved off the main thread to
  a bounded Web Worker pool (File handles by reference); vitest gate
  asserts the pool beats sequential (first gate draft posting buffers
  was 2.6x slower and was rewritten — copies dominated).

Validation: cargo fmt + clippy -D warnings clean; 514 unit + 544
integration tests green; 270 frontend tests green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CBK1RdtzyP6759Muqe1K1w

src/interfaces/api/handlers/file_handler.rs

@@ -12,7 +12,7 @@ use std::collections::HashMap;
 use utoipa::ToSchema;
 
 use crate::application::ports::file_ports::{
-    FileManagementUseCase, FileRetrievalUseCase, FileUploadUseCase,
+    FileManagementUseCase, FileRetrievalUseCase, FileUploadUseCase, RangeContent,
 };
 use crate::application::ports::storage_ports::{FileReadPort, StorageUsagePort};
 use crate::application::ports::thumbnail_ports::ThumbnailPort;
@@ -713,10 +713,19 @@ impl FileHandler {
                         Self::content_disposition(&file_dto.name, &file_dto.mime_type, &params);
 
                     match retrieval
-                        .get_file_range_stream_with_perms(&id, auth_user.id, start, Some(end + 1))
+                        .get_file_range_preloaded_with_perms(
+                            &file_dto,
+                            auth_user.id,
+                            start,
+                            Some(end + 1),
+                        )
                         .await
                     {
-                        Ok(stream) => {
+                        Ok(content) => {
+                            let body = match content {
+                                RangeContent::Bytes(b) => Body::from(b),
+                                RangeContent::Stream(s) => Body::from_stream(Box::into_pin(s)),
+                            };
                             return Response::builder()
                                 .status(StatusCode::PARTIAL_CONTENT)
                                 .header(header::CONTENT_TYPE, &*file_dto.mime_type)
@@ -732,7 +741,7 @@ impl FileHandler {
                                     header::CACHE_CONTROL,
                                     "private, max-age=3600, must-revalidate",
                                 )
-                                .body(Body::from_stream(Box::into_pin(stream)))
+                                .body(body)
                                 .unwrap()
                                 .into_response();
                         }