fix(downloads): a download larger than the space left says so, not "processing failed"

yt-dlp refuses a file announced over `max_filesize` by logging one line and returning with no file
(measured, and pinned in test_formats against a local server): the worker found no output and
failed the job as `postprocess`. `formats.watching_size_cap` now sees that line through our yt-dlp
logger, and the download (and, should it ever happen, a YouTube clip's range fetch) fails as the
owner's refusal with DOWNLOAD_TOO_BIG_MESSAGE, classified `quota_exceeded`. The download's quota
copy says it does not fit in what is left — true at a full cap too — instead of "Storage full".
A pre-existing type error the change touched is fixed (baseline down by one).

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

@@ -307,8 +307,8 @@
           "body": "Something went wrong with this download. The technical details below may help."
         },
         "quota_exceeded": {
-          "short": "Storage full",
-          "body": "This download was stopped because your storage quota is already used up. Delete something from your library, then try again."
+          "short": "Not enough storage",
+          "body": "This download doesn't fit in the storage you have left. Delete something from your library, then try again."
         }
       },
       "catalog": {

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

@@ -307,8 +307,8 @@
           "body": "Valami hiba történt ennél a letöltésnél. Az alábbi technikai részletek segíthetnek."
         },
         "quota_exceeded": {
-          "short": "Betelt a tárhely",
-          "body": "Ez a letöltés leállt, mert a tárhelykereted már elfogyott. Törölj valamit a könyvtáradból, aztán próbáld újra."
+          "short": "Nincs elég tárhely",
+          "body": "Ez a letöltés nem fér bele a megmaradt tárhelyedbe. Törölj valamit a könyvtáradból, aztán próbáld újra."
         }
       },
       "catalog": {

frontend/src/lib/downloadFailure.test.ts

@@ -81,13 +81,31 @@ describe("failTitleKey", () => {
       expect(i18n.t(failCopyKeys(download, "body"))).toBe(
         i18n.t("downloads.errors.fail.cat.quota_exceeded.body"),
       );
-      // Its headline too: space is left, so not "Storage full".
+      // Its headline too, worded for the converted file rather than the download it is not.
       const short = i18n.t(failCopyKeys(upload, "short"));
       expect(short).not.toMatch(/^downloads\./);
       expect(short).not.toBe(i18n.t("downloads.errors.fail.cat.quota_exceeded.short"));
     }
   });
 
+  it("a download refused for storage says it does not fit, true with space left or none", async () => {
+    // Refused at a full cap before it starts, or by yt-dlp for a file larger than what is left: one
+    // sentence true of both, so never "full" or "used up".
+    const download = {
+      error_code: "quota_exceeded",
+      error_detail: null,
+      job_kind: "download",
+    } as const;
+    for (const lng of ["en", "hu"]) {
+      await i18n.changeLanguage(lng);
+      for (const part of ["short", "body"] as const) {
+        const text = i18n.t(failCopyKeys(download, part));
+        expect(text).not.toMatch(/^downloads\./);
+        expect(text).not.toMatch(/full|used up|betelt|elfogyott/i);
+      }
+    }
+  });
+
   it("a clip refused for storage says so of a clip, and not that the quota is used up", async () => {
     // Refused before it is cut (nothing left) or after (the cut is bigger than what is left): one
     // sentence true of both, worded for a clip and naming the clip-side way out.