feat(upload): batch dedup-check + instant uploads + resilient parallel uploads

Backend:
- POST /api/dedup/check-batch — returns the subset of submitted whole-file
  BLAKE3 hashes the caller already owns, in one query (user-scoped,
  anti-enumeration via idx_files_blob_hash). Lets a client learn which of N
  files it can skip with a single round trip.
  (dedup_service::user_owned_blob_references, dedup_handler, routes) + tests.

Frontend — upload pipeline:
- Instant ("by-hash") upload for content the caller already owns: hash every
  in-band file, ONE /api/dedup/check-batch, create the owned ones with zero
  content bytes, upload only the rest. Covers all sizes below the 8 MB delta
  threshold (delta handles larger files). vendor/hashWasm computes the
  whole-file BLAKE3 on the main thread.
- Resilient parallel uploads: bounded concurrency (4) + a per-file deadline,
  so one stuck/slow/failing file no longer freezes the whole batch — it blocks
  only its own lane and times out / is skipped while the rest proceed. Quota
  exhaustion stops the run early; partial results are reported ("N uploaded,
  M failed").
- Folder uploads (uploadTree) show live bell progress + a final result and go
  through the same dedup + parallel pipeline.
- Storage bar ("Almacenamiento") refreshes after uploads/deletes
  (session.refresh) instead of showing the stale login value.

Frontend — i18n / UI fixes:
- Fix literal {{count}} and {{percentage}}/{{used}}/{{total}} (param-name
  mismatches) in the selection toolbar and storage line; add es strings.
- Remove the underline on user-menu link rows.

Benchmark (uploadStrategies.bench.test.ts) compares baseline / per-file / batch:
the batch collapses N per-file probes into one check (e.g. a WAN 1000-file run
drops from 1700 to 1001 round trips) while matching per-file's byte savings.

Also includes in-progress group virtual-description i18n work present in the
working tree (groups.ts, ResourceList, locale `groups` keys).

Verified: cargo clippy -D warnings (clean), backend 448 tests; frontend
npm run check (clean), 58 unit tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/static/locales/es.json

@@ -367,7 +367,9 @@
     "share": "Compartir",
     "view": "Ver",
     "selected_count": "{{count}} seleccionados",
-    "uploaded_saved": "Subida completa — {{mb}} MB deduplicados"
+    "uploaded_saved": "Subida completa — {{mb}} MB deduplicados",
+    "uploaded_partial": "{{ok}} subidos, {{failed}} fallaron",
+    "upload_failed": "La subida falló"
   },
   "dialogs": {
     "rename_folder": "Renombrar carpeta",