v2.1.2 — X-Robots-Tag noindex on every response

Search-engine noindex hardening.

Added

• X-Robots-Tag: noindex, nofollow on every viewer response (SEC_HEADERS) — the existing robots meta only covers HTML; the header extends the no-indexing guarantee to every response the viewer emits, including error pages
• Robots meta upgraded from noindex to noindex, nofollow to match the header