refactor(i18n): ask the catalogue for a sentence in one helper

`t()` answers a missing key with the key, so "does this code have a
sentence" was a comparison written inline at every site that wanted a
code's sentence or a fallback, twenty-odd times in several spellings.
translateOrNull, translateCodeOrNull and translateCode in
src/lib/i18n/translate-code.ts now hold that probe, every site uses
them, and a guard refuses the inline comparison anywhere else.

src/components/settings/account-section/index.tsx

@@ -58,6 +58,7 @@ import {
 import { AvatarSection } from "./avatar-section";
 import { SetupCard } from "./setup-card";
 import { dateOnlyKey } from "@/lib/tz/date-only";
+import { translateCodeOrNull } from "@/lib/i18n/translate-code";
 
 export { resolveInitialTimezone } from "./account-section-utils";
 
@@ -368,10 +369,7 @@ export function AccountSection() {
       setFieldErrors(describeRejectedProfileFields(json?.details?.issues, t));
       if (errorCode === "profile.update.nothingSaved" && field) {
         setSaveMsg({ key: "settings.profileNothingSaved", params: { field } });
-      } else if (
-        errorCode &&
-        t(`apiErrors.${errorCode}`) !== `apiErrors.${errorCode}`
-      ) {
+      } else if (translateCodeOrNull(t, "apiErrors", errorCode) !== null) {
         // Only a code with a sentence of its own: every refusal carries a
         // code now, and the generic `http.*` family has no translation.
         setSaveMsg({ key: `apiErrors.${errorCode}` });

src/components/settings/integrations/integration-actions.tsx

@@ -30,6 +30,7 @@ import {
   useSyncOutcomeMessage,
   type SyncOutcomeState,
 } from "./sync-outcome";
+import { translateCode } from "@/lib/i18n/translate-code";
 
 export interface ProviderSync {
   syncing: boolean;
@@ -151,11 +152,12 @@ export function ActionResultLines({
   const { t } = useTranslations();
 
   function describeError(errorCode: string): string {
-    const key = `settings.testConnection.errors.${errorCode}`;
-    const translated = t(key);
-    return translated === key
-      ? t("settings.testConnection.errors.generic")
-      : translated;
+    return translateCode(
+      t,
+      "settings.testConnection.errors",
+      errorCode,
+      "settings.testConnection.errors.generic",
+    );
   }
 
   const busy = sync?.syncing || test?.testing;

src/components/settings/ntfy-card.tsx

@@ -22,6 +22,7 @@ import {
 import { useTranslations } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
 import { apiFetchRaw, apiGet } from "@/lib/api/api-fetch";
+import { translateCodeOrNull } from "@/lib/i18n/translate-code";
 
 interface NtfySettings {
   enabled: boolean;
@@ -80,13 +81,13 @@ export function NtfyCard({ isAuthenticated }: { isAuthenticated: boolean }) {
         };
         // A coded refusal (the private-origin policy) translates like the
         // test button's; anything else shows the server sentence.
-        const code = json.meta?.errorCode;
-        const key = code ? `settings.testConnection.errors.${code}` : null;
-        const translated = key ? t(key) : null;
         throw new Error(
-          translated && translated !== key
-            ? translated
-            : json.error || t("common.error"),
+          translateCodeOrNull(
+            t,
+            "settings.testConnection.errors",
+            json.meta?.errorCode,
+          ) ??
+            (json.error || t("common.error")),
         );
       }
     },

src/components/settings/test-connection-button.tsx

@@ -6,6 +6,7 @@ import { CheckCircle2, Loader2, Plug, XCircle } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { useTranslations } from "@/lib/i18n/context";
 import { apiFetchRaw } from "@/lib/api/api-fetch";
+import { translateCode } from "@/lib/i18n/translate-code";
 
 /**
  * Shared "Test connection" UX for the settings integrations + notifications
@@ -151,13 +152,12 @@ export function TestConnectionButton({
   }
 
   function describeError(errorCode: string): string {
-    const key = `settings.testConnection.errors.${errorCode}`;
-    const translated = t(key);
-    // `t()` returns the raw key when missing — fall back to generic.
-    if (translated === key) {
-      return t("settings.testConnection.errors.generic");
-    }
-    return translated;
+    return translateCode(
+      t,
+      "settings.testConnection.errors",
+      errorCode,
+      "settings.testConnection.errors.generic",
+    );
   }
 
   return (

src/components/settings/webhook-card.tsx

@@ -24,6 +24,7 @@ import { useTranslations } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
 import { apiFetchRaw, apiGet } from "@/lib/api/api-fetch";
 import type { WebhookPayloadFormat } from "@/lib/notifications/types";
+import { translateCodeOrNull } from "@/lib/i18n/translate-code";
 
 interface WebhookSettings {
   enabled: boolean;
@@ -89,13 +90,13 @@ export function WebhookCard({ isAuthenticated }: { isAuthenticated: boolean }) {
         };
         // A coded refusal (the private-origin policy) translates like the
         // test button's; anything else shows the server sentence.
-        const code = json.meta?.errorCode;
-        const key = code ? `settings.testConnection.errors.${code}` : null;
-        const translated = key ? t(key) : null;
         throw new Error(
-          translated && translated !== key
-            ? translated
-            : json.error || t("common.error"),
+          translateCodeOrNull(
+            t,
+            "settings.testConnection.errors",
+            json.meta?.errorCode,
+          ) ??
+            (json.error || t("common.error")),
         );
       }
     },