Stream uploads directly into the CDC chunk store (no spool, single write)

Every upload surface previously wrote each byte to disk twice: the HTTP
body was spooled to a temp file (or assembled from chunk parts), then
mmap-re-read for FastCDC analysis, and finally the new chunks were
written to the blob backend. CDC could not start until the last byte
arrived, so large uploads paid receive + reread + rewrite latency.

The dedup engine now chunks, hashes and settles the stream WHILE it
arrives (fastcdc AsyncStreamCDC + incremental BLAKE3):

- Each batch of distinct chunks is pinned-or-classified by ONE
  `UPDATE … RETURNING` (no check-then-bump TOCTOU; pinned chunks can't
  be reclaimed mid-upload), and only chunks the store doesn't have are
  written — a full dedup hit performs zero content writes.
- Durability before visibility is preserved: one batched fsync sweep,
  then one batched INSERT, then the manifest. Identical concurrent
  uploads are resolved at the manifest INSERT via ON CONFLICT (the
  loser releases its references and becomes a dedup hit).
- A drop guard rolls back pins and surfaces written-but-unregistered
  chunks to GC if the request future is cancelled mid-stream.
- MIME sniffing now peeks the first bytes in-flight; client-requested
  MD5/SHA-256 checksums are computed by a stream tee — the post-upload
  re-read of the assembled file is gone.

All surfaces converge on the new interfaces::upload_ingest helper:
REST multipart, WebDAV PUT, NextCloud PUT, WOPI PutFile, the dedup
endpoint, and both chunked-upload completions (which now stream their
ordered parts straight into the store instead of writing an assembled
file — chunk parts persist until finalize, so completion is genuinely
retryable). The legacy blob re-chunk migration streams from the
backend with no spool file either.

Legacy removed: store_from_file + mmap CDC analysers + temp-path
plumbing through every port (pre_computed_hash, save_file_from_temp,
update_file_content_from_temp), upload_spool + assembled-file
assembly in both chunked services, create_file/update_file byte-slice
variants (no callers), common::temp, the OXICLOUD_UPLOAD_TMPDIR
config, and the memmap2 dependency.

Verified end-to-end against PostgreSQL 16: 8 MB upload (26 chunks),
identical re-upload (dedup hit, zero writes), 3-byte edit re-upload
(26 chunks, 1 written), byte-identical downloads, Range across chunk
boundaries, concurrent identical-upload race (manifest ref 2), and
trash-empty reclaiming exactly the unshared chunk while the shared 25
survive for the edited file. The empty/sub-8KB multipart path found a
post-EOF re-poll panic in the MIME peek (fixed with fuse + regression
test).

https://claude.ai/code/session_01WdNenpnujNR2sc32XVvwfS

docs/config/env.md

@@ -14,8 +14,7 @@ Most runtime variables use the `OXICLOUD_` prefix. A few build-time or allocator
 | `OXICLOUD_MAX_UPLOAD_SIZE` | `10737418240` | Whole-file size ceiling, in bytes (10 GB on 64-bit, 1 GB on 32-bit). Applies to BOTH direct PUTs (per-request body) and chunked uploads (declared `total_size`, checked upfront at session creation). |
 | `OXICLOUD_DIRECT_PUT_MAX_BYTES` | `1073741824` | Per-request cap for non-chunked PUT bodies, in bytes (1 GiB). Set below `OXICLOUD_MAX_UPLOAD_SIZE` so larger files are pushed onto the chunked protocol (resumable on failure). See [Storage Fine Tuning](./storage-fine-tuning.md). |
 | `OXICLOUD_CHUNK_MAX_BYTES` | `104857600` | Maximum size of a single chunked-upload PUT in bytes (100 MB). Per-chunk cap, independent of `OXICLOUD_MAX_UPLOAD_SIZE` (whole-file cap). See [Storage Fine Tuning](./storage-fine-tuning.md). |
-| `OXICLOUD_UPLOAD_TMPDIR` | (OS temp dir) | Spool directory for non-chunked PUT bodies (`/api/files/upload`, WebDAV PUT). Point at a real-disk path on the same FS as `.blobs/` to avoid tmpfs OOMKill and make blob promotion an atomic rename. See [Storage Fine Tuning](./storage-fine-tuning.md). |
-| `OXICLOUD_CHUNK_DIR` | `{STORAGE_PATH}/.uploads` | Root directory for chunked-upload sessions (REST + NextCloud). Same-FS / NVMe placement guidance: see [Storage Fine Tuning](./storage-fine-tuning.md). |
+| `OXICLOUD_CHUNK_DIR` | `{STORAGE_PATH}/.uploads` | Root directory for chunked-upload sessions (REST + NextCloud). Direct (non-chunked) uploads stream straight into the blob store and need no spool directory. Placement guidance: see [Storage Fine Tuning](./storage-fine-tuning.md). |
 | `OXICLOUD_REUSE_PORT` | `false` | Enable `SO_REUSEPORT` so multiple processes can share the same port. **Disabled by default** — a second accidental instance will fail with "address already in use". Enable only for deliberate multi-worker setups (process supervisor, rolling restart). Not supported on Windows. |
 
 ## Database