feat(translate): multi-file queue with dedicated runner tests + context polish

Batch upload: dropzone and inputs accept multiple files (cap 10/run,
validated + deduped); 2+ files switch the submit to a queue screen —
sequential jobs with per-file progress, failure messages through the
humanizer, per-file download/review links, staggered download-all,
real server-side stop (cancel API) plus between-files abort. The
one-file flow is untouched: files.length === 1 takes the exact
existing path.

Runner: standalone runTranslationJob (submit + poll + abort + cancel)
with injectable poll interval; 5 dedicated vitest cases covering
completed-with-progress, backend failure, submit HTTP error, mid-flight
abort with server cancel, and network-failure cutoff.

Context page close review: /dashboard/context is a clean redirect to
glossaries (no duplicate); the fake 300ms save delay removed (instant
zustand persist); suggestion chips now resolve their prompt bodies
through i18n (EN+FR — no more French prompts for English users); the
translate config column shows a 'Context guidelines active' chip that
links to the editor when a Pro LLM prompt is set.

Dead code: legacy file-uploader.tsx (+webllm.ts, its only consumer)
and the unused PRESETS/applyPreset/clearContext store block removed
(-14KB of glossary strings).

Verified: build exit 0, vitest 14/14 (9 prior + 5 runner), eslint 62
errors (vs 64 at HEAD), 0 missing i18n keys.

frontend/src/app/dashboard/translate/useTranslationSubmit.ts

@@ -63,7 +63,7 @@ function persistActiveJob(job: StoredJob | null) {
   } catch { /* storage unavailable — session-only fallback */ }
 }
 
-function pushRecentJob(job: RecentJob) {
+export function pushRecentJob(job: RecentJob) {
   try {
     const list = getRecentJobs().filter(j => j.jobId !== job.jobId);
     list.unshift(job);