fix: honest costs in streams, oracle-sized timeouts, history & log cleanup

Cost showed $0 for every streamed request: the X-Cortiq-Cost-USD header is
written before generation, when the cost cannot be known. The gateway now
ships the final number in a closing SSE event (`cortiq_cost_usd`, alongside
the token estimate when the provider sent no usage), and the console prefers
it over the header. Money renders with 4 decimals, the last two in a smaller
font — $0.0006 stays readable instead of collapsing to $0.

Timeouts, both ends: the router default was 800 ms, silently degrading every
prompt the hosted router escalates to its oracle (~10 s) — now 15 s. Provider
clients had NO timeout at all (a dead OpenRouter host hung requests forever) —
now a 10 s connect timeout, with no overall cap so long generations and
streams are never cut.

Benchmark history: per-run × and a Clear-all button. Logs view: a clear
button backed by DELETE /admin/api/logs.

web/js/i18n/de.js

@@ -601,4 +601,5 @@ export default {
   "bm.liveRunning": "läuft…",
   "bm.spent": "ausgegeben",
   "bm.verdict": "🏁 Fertig: Antworten {p}, ausgegeben {s}",
+  "bm.clearHistory": "Alle löschen",
 };

web/js/i18n/en.js

@@ -594,4 +594,5 @@ export default {
   "bm.liveRunning": "running…",
   "bm.spent": "spent",
   "bm.verdict": "🏁 Done: answers {p}, spent {s}",
+  "bm.clearHistory": "Clear all",
 };

web/js/i18n/es.js

@@ -601,4 +601,5 @@ export default {
   "bm.liveRunning": "en curso…",
   "bm.spent": "gastado",
   "bm.verdict": "🏁 Listo: respuestas {p}, gastado {s}",
+  "bm.clearHistory": "Borrar todo",
 };

web/js/i18n/fr.js

@@ -601,4 +601,5 @@ export default {
   "bm.liveRunning": "en cours…",
   "bm.spent": "dépensé",
   "bm.verdict": "🏁 Terminé : réponses {p}, dépensé {s}",
+  "bm.clearHistory": "Tout effacer",
 };

web/js/i18n/ru.js

@@ -593,4 +593,5 @@ export default {
   "bm.liveRunning": "идёт…",
   "bm.spent": "потрачено",
   "bm.verdict": "🏁 Готово: ответы {p}, потрачено {s}",
+  "bm.clearHistory": "Очистить всё",
 };

web/js/i18n/tr.js

@@ -601,4 +601,5 @@ export default {
   "bm.liveRunning": "sürüyor…",
   "bm.spent": "harcanan",
   "bm.verdict": "🏁 Bitti: yanıtlar {p}, harcanan {s}",
+  "bm.clearHistory": "Tümünü temizle",
 };

web/js/i18n/zh.js

@@ -601,4 +601,5 @@ export default {
   "bm.liveRunning": "进行中……",
   "bm.spent": "花费",
   "bm.verdict": "🏁 完成：回答 {p}，花费 {s}",
+  "bm.clearHistory": "全部清除",
 };