fix(reports): header 「生成报告」 joins the report disabled-button rule (BUG-1078)

The generate button renders in SecondaryPageShell's actions slot, outside the
report roots, so while submitting it still got the global 45% fade. A
report-owned `report-center-generate` class brings it into the disabled rule;
SecondaryPageShell and button.tsx unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017eEAG8HD3mm8gsKXgk8uU8

frontend/src/components/personal-report/generate-personal-report-button.tsx

@@ -207,7 +207,7 @@ export function GeneratePersonalReportButton({
       type="button"
       variant="outline"
       size="sm"
-      className="shrink-0 whitespace-nowrap"
+      className="report-center-generate shrink-0 whitespace-nowrap"
       onClick={() => void handleGenerate()}
       disabled={submitting}
       title="根据已保存的具体出生分钟生成完整报告；未校正会标明方向性参考"