feat(diagnostics): send a bug report to a private Gitea issue tracker (E16 S4)

- admin config group "Bug reports": Gitea address, repository, token (secret),
  and "Check the connection" — the repository must answer, take issues and
  be PRIVATE (a report carries its reporter's log); checked on every send too
- POST /api/debug-sessions/{id}/issue sends the SAVED draft: create the issue,
  upload each file on its own request (the measured API), then show the
  screenshots inline; progress is kept in the draft, so a send that stops
  half-way keeps its issue and the retry sends only what is missing; 5 new
  issues an hour per user; audited as issue_create
- the composer: Create issue (only where a tracker is set up, naming the
  repository), a partial-send banner with retry, and a Preview — the tracker's
  own rendering in a sandboxed frame, or the zip's markdown without one
- the recorder's refusals answer in the localized family (debug_session_*,
  screenshot_*, issue(s)_*), not bare codes the UI could only call generic
- a tracker refusal logs the status only: its message can quote the title back

frontend/src/components/ConfigPanel.tsx

@@ -134,6 +134,14 @@ export default function ConfigPanel() {
       notifyActionError(e, t("config.plexTestFailed"));
     },
   });
+  // Bug reports' "Check the connection" (E16): the repository answers, takes issues, is private.
+  const testIssues = useMutation({
+    mutationFn: () => api.testIssues(),
+    onSuccess: (r) =>
+      notify({ level: "success", message: t("config.issuesTestOk", { repo: r.repo }) }),
+    onError: (e) => notifyActionError(e, t("config.issuesTestFailed")),
+  });
+
   const plexLibs = (draft["plex_libraries"] ?? "")
     .split(",")
     .map((s) => s.trim())
@@ -218,6 +226,22 @@ export default function ConfigPanel() {
               </div>
             )}
 
+            {activeGroup === "issues" && (
+              <div className="mt-3 pt-3 border-t border-border/60">
+                <Tooltip hint={t("config.issuesTestHint")}>
+                  <FocusSafeButton
+                    onClick={() => testIssues.mutate()}
+                    disabled={testIssues.isPending || dirty}
+                    className="glass-card glass-hover inline-flex items-center gap-2 px-3 py-2 rounded-xl text-sm disabled:opacity-50 transition"
+                  >
+                    <Plug className={`w-4 h-4 ${testIssues.isPending ? "animate-pulse" : ""}`} />
+                    {t("config.issuesTest")}
+                  </FocusSafeButton>
+                </Tooltip>
+                {dirty && <p className="text-2xs text-muted mt-2">{t("config.plexTestDirty")}</p>}
+              </div>
+            )}
+
             {activeGroup === "plex" && (
               <div className="mt-3 pt-3 border-t border-border/60">
                 <Tooltip hint={t("config.plexTestHint")}>