feat(ui): the continuous complexity score shows next to the tier

Benchmark (routing mode) and the dashboard's recent-requests list now print
the router's raw 0..1 score under/next to the tier badge — people can see
what different prompts actually weigh and tune the boundary sliders from
real data. Tooltip explains the link to the Routing sliders (7 languages).

Caught before commit: naming the field row.score collided with the answer-
correctness fraction from evaluate() and dragged the benchmark's quality KPI
down to the average complexity — renamed to cscore, KPI verified back at
100%. Dashboard tier badges also render translated names now, and the
Russian locale calls the dashboard «Рабочий стол».

web/js/i18n/fr.js

@@ -634,4 +634,5 @@ export default {
   "tier.low": "facile",
   "tier.medium": "moyen",
   "tier.high": "difficile",
+  "bm.scoreHint": "Le score de complexité continu du routeur (0..1) — les curseurs de limites de la page Routage le découpent en niveaux.",
 };