Add GDPR cookie-consent banner (Consent Mode v2)

- consent.js: self-contained, non-blocking bottom banner in EN/MK/SI,
  remembers the choice in localStorage, links to the per-language cookie
  policy. Accept -> gtag consent 'update' granted; Decline stays denied.
- Head GA snippet restores a returning visitor's prior "granted" choice
  before the first hit; loads /consent.js on every page.
- Re-openable via window.msosOpenConsent() for a "manage cookies" link.

Verified in-browser: shows for new visitors, Accept grants + remembers,
reload keeps consent without re-prompting, Slovene text + /si/ policy link.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tools/seo_inject.py

@@ -85,9 +85,14 @@ GA_LINES = [
     "        ad_storage: 'denied', ad_user_data: 'denied', ad_personalization: 'denied',",
     "        analytics_storage: 'denied', wait_for_update: 500",
     "      });",
+    "      // Restore a returning visitor's prior choice before the first hit.",
+    "      try { if (localStorage.getItem('msos-consent') === 'granted') {",
+    "        gtag('consent', 'update', { ad_storage:'granted', ad_user_data:'granted',",
+    "          ad_personalization:'granted', analytics_storage:'granted' }); } } catch(e){}",
     "      gtag('js', new Date());",
     f"      gtag('config', '{GA_ID}');",
     '    </script>',
+    '    <script src="/consent.js" defer></script>',
 ]
 
 # ---- page trees (for hreflang parity) ----