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/lib/api/account.ts

@@ -35,6 +35,8 @@ export interface Me {
   diagnostics: DiagnosticsState;
   /** The debug session recording right now, if any (E16) — a reload resumes it. */
   debug_session: DebugSession | null;
+  /** Where a bug report goes — the tracker's repository — or null: download only (E16 S4). */
+  issues: { repo: string } | null;
 }
 
 /** The `nav.role.*` key an account is shown under. Demo isn't a real role (it's a flag on a `user`