fix(scheduler,i18n): a failure a job names reads in the reader's language

The audit log showed a failed RSS poll as the server's English sentence
under a Hungarian UI. A job can now raise progress.JobFailed(reason,
message, **params): the scheduler stores the reason and params as the
run's data (dashboard, manual-run notice, audit row) beside the English
line, and the client renders scheduler.failure.<reason>. The RSS outage
names its first channel and the reason code (HTTP 404 vs unreachable).
An upstream's own error text stays as raised (diagnostic).

frontend/src/components/Scheduler.tsx

@@ -35,7 +35,7 @@ import { useContextMenu } from "./ui/useContextMenu";
 import { ContextMenu } from "./ui/ContextMenu";
 import { MoreButton } from "./ui/MoreButton";
 import { type ActionMenuItem } from "./ui/ActionMenu";
-import { jobResultText } from "../lib/jobResult";
+import { jobFailureText, jobResultText } from "../lib/jobResult";
 
 const POLL_MS = 4000;
 // While any job is running, poll faster so short scheduled runs aren't missed between ticks.
@@ -257,7 +257,10 @@ function JobRow({
               ? t("scheduler.lastRun", { time: relativeTime(job.last_finished, lang) })
               : t("scheduler.neverRun")}
           {job.last_error ? (
-            <span className="text-danger"> · {job.last_error}</span>
+            <span className="text-danger">
+              {" · "}
+              {jobFailureText(t, job.result, lang) ?? job.last_error}
+            </span>
           ) : job.result ? (
             <span> · {jobResultText(t, job.result, lang)}</span>
           ) : job.last_result ? (

frontend/src/i18n/locales/en/scheduler.json

@@ -186,5 +186,14 @@
     "lowquota": "low quota",
     "noreadscope": "no YouTube read access",
     "busy": "another sync is running"
+  },
+  "failure": {
+    "rss_all_failed": "The RSS feed answered for none of the {{total}} channels — the first: {{channel}}, {{cause}}. Read through the API instead: {{read}}"
+  },
+  "rssCause": {
+    "http": "HTTP {{status}}",
+    "transport": "unreachable",
+    "apply": "could not be saved",
+    "error": "unexpected error"
   }
 }

frontend/src/i18n/locales/hu/scheduler.json

@@ -186,5 +186,14 @@
     "lowquota": "kevés a kvóta",
     "noreadscope": "nincs YouTube-olvasási jogosultság",
     "busy": "egy másik szinkron fut"
+  },
+  "failure": {
+    "rss_all_failed": "Az RSS-hírcsatorna egyik csatornánál sem válaszolt ({{total}}) — az első: {{channel}}, {{cause}}. Az API-n át beolvasva helyette: {{read}}"
+  },
+  "rssCause": {
+    "http": "HTTP {{status}}",
+    "transport": "nem érhető el",
+    "apply": "nem sikerült menteni",
+    "error": "váratlan hiba"
   }
 }

frontend/src/lib/jobResult.dom.test.ts

@@ -4,7 +4,7 @@
 // one-liner was "recent={'channels_processed': 0, …}, deep={…}" — English keys and a Python repr.
 import { afterEach, describe, expect, it } from "vitest";
 import i18n, { setLanguage } from "../i18n";
-import { jobResultText, parseSummary } from "./jobResult";
+import { jobFailureText, jobResultText, jobRunText, parseSummary } from "./jobResult";
 
 afterEach(() => setLanguage("en"));
 
@@ -65,3 +65,34 @@ describe("an older notice's one-liner", () => {
     expect(parseSummary(null)).toBeNull();
   });
 });
+
+// E31: the audit log showed a failed RSS poll as the server's English sentence ("RSS poll failed for
+// all 399 channels — first: …") under a Hungarian UI. A failure the job names rides along as data.
+describe("a failed run", () => {
+  const run = {
+    job_id: "rss_poll",
+    status: "error",
+    summary:
+      "RSS poll failed for all 399 channels — first: UCx: RSS fetch for UCx returned HTTP 404",
+    result: { failure: "rss_all_failed", total: 1399, channel: "UCx", cause: "http_404", read: 0 },
+  };
+
+  it("says the failure the job named in the reader's language", () => {
+    const t = i18n.getFixedT("hu");
+    expect(jobRunText(t, run, "hu").body).toBe(
+      "Az RSS-hírcsatorna egyik csatornánál sem válaszolt (1399) — az első: UCx, HTTP 404. " +
+        "Az API-n át beolvasva helyette: 0",
+    );
+    expect(jobFailureText(t, { ...run.result, cause: "transport" }, "hu")).toContain(
+      "UCx, nem érhető el.",
+    );
+  });
+
+  it("keeps any other failure's own text", () => {
+    const t = i18n.getFixedT("hu");
+    expect(jobRunText(t, { ...run, summary: "Plex returned 500", result: null }, "hu").body).toBe(
+      "Plex returned 500",
+    );
+    expect(jobFailureText(t, { failure: "moon_is_full" }, "hu")).toBeNull();
+  });
+});

frontend/src/lib/jobResult.ts

@@ -38,10 +38,30 @@ export function jobResultText(t: TFunction, result: JobResult, lang: string): st
     .join(" · ");
 }
 
+/** A failure the job named (the server's `progress.JobFailed`: `{failure: <reason>, …params}`) in the
+ *  reader's language (E31); null for any other failure, which keeps the upstream's own text. */
+export function jobFailureText(t: TFunction, result: unknown, lang: string): string | null {
+  if (!result || typeof result !== "object") return null;
+  const { failure, ...params } = result as Record<string, unknown>;
+  if (typeof failure !== "string") return null;
+  const values: Record<string, string> = {};
+  for (const [k, v] of Object.entries(params))
+    values[k] = typeof v === "number" ? formatNumber(v, lang) : String(v);
+  if (typeof params.cause === "string") values.cause = rssCause(t, params.cause);
+  return t(`scheduler.failure.${failure}`, { ...values, defaultValue: "" }) || null;
+}
+
+/** Why a feed did not answer, from the poll's reason code (`http_404`, `transport`, …). */
+function rssCause(t: TFunction, cause: string): string {
+  const http = /^http_(\d+)$/.exec(cause);
+  if (http) return t("scheduler.rssCause.http", { status: http[1] });
+  return t(`scheduler.rssCause.${cause}`, { defaultValue: cause });
+}
+
 /** What a job run said, as the inbox notice and the audit row both show it (E30): a title naming the job
  *  and how the run ended, and its result in the reader's language — from the data when it rode along,
- *  else read back from the English one-liner. A skipped run names only why; a failed run keeps the
- *  upstream's own error text (it is diagnostic). */
+ *  else read back from the English one-liner. A skipped run names only why; a failed run says the
+ *  failure the job named (`jobFailureText`, E31), else keeps the upstream's own text (diagnostic). */
 export function jobRunText(
   t: TFunction,
   run: { job_id: string; status?: unknown; summary?: unknown; result?: unknown },
@@ -65,10 +85,12 @@ export function jobRunText(
   }
   // A skipped run's title already says "skipped": its body is only the reason, not "skipped: <reason>".
   const reason = run.status === "skipped" ? onlySkipReason(result) : null;
+  const failure = run.status === "error" ? jobFailureText(t, run.result, lang) : null;
   return {
     title: t(titleKey, { job }),
-    body:
-      reason !== null
+    body: failure
+      ? failure
+      : reason !== null
         ? t(`scheduler.skip.${vocabKey(reason)}`, { defaultValue: reason })
         : result
           ? jobResultText(t, result, lang)