fix(ui): a write that fails says what failed and why, wherever it fails

`req` opens its blocking dialog for 400/409/422/5xx only. A 403/404/429 was left to the caller and a
502-504 or lost connection got just the self-clearing connection notice, so 34 mutations without a
reporting onError and 15 direct api writes with a bare or missing catch failed in silence: a hidden
channel that snapped back, a share link that never revoked, a confirmed account delete that ended
with nothing said.

- lib/queryClient: one MutationCache reporter. react-query awaits it BEFORE the mutation's own
  onError, so it waits a task and skips a failure the site already reported; the toast title comes
  from `meta.failTitle`, `meta.errorShownInline` opts out.
- notifyActionError: title names WHAT failed, the line under it says WHY (`failureReason`: a
  structured localized detail, else the status). It marks the error reported (`markReported`), so
  nothing reports one failure twice; `notifyKnownFailure` for a site's own specific sentence.
- Every silent site named (45 new HU/EN titles, 4 reasons). Stale "the global dialog shows it"
  comments corrected on the job actions, channel block, Plex sync, cookies, download enqueue,
  account delete and usePref.
- Channels passed the tag hook's channel id to the reporter as the error; the tag and priority hooks
  now report themselves, with the real error.
- A contract test keeps every useMutation naming its failure; CLAUDE.md gains the pattern row.
- history.dom.test: the "navigates only once the entries are back" assertion raced an async act's
  macrotask flush (1 in 5 runs); it now asserts from a later popstate listener.

frontend/src/components/ShareDialog.tsx

@@ -106,15 +106,18 @@ function LinkRow({ link, onChanged }: { link: ShareLink; onChanged: () => void }
   const toggle = useMutation({
     mutationFn: () => api.updateDownloadLink(link.id, { allow_download: !link.allow_download }),
     onSuccess: onChanged,
+    meta: { failTitle: "errors.writeFailed.shareLinkDownload" },
   });
   const revoke = useMutation({
     mutationFn: () => api.revokeDownloadLink(link.id),
     onSuccess: onChanged,
+    meta: { failTitle: "errors.writeFailed.shareLinkRevoke" },
   });
   // Set / change / clear the link password. Rotating (or clearing) it bumps the link's
   // password_version server-side, which invalidates any watch grant issued under the old password.
   const savePass = useMutation({
     mutationFn: (pw: string) => api.updateDownloadLink(link.id, { password: pw }),
+    meta: { failTitle: "errors.writeFailed.shareLinkPassword" },
     onSuccess: () => {
       setEditPass(false);
       setNewPass("");
@@ -282,6 +285,7 @@ function LinkShare({ job }: { job: DownloadJob }) {
       setExpiryDays(null);
       setPassword("");
     },
+    meta: { failTitle: "downloads.share.linkFailed" },
   });
 
   // Open with a link already generated: sharing is almost always the goal, so mint a default