Add HSTS header at the origin (host-scoped, no includeSubDomains)

nginx/security-headers.conf

@@ -2,8 +2,10 @@
 # that sets its own add_header (because add_header in a location REPLACES, not
 # merges, inherited headers — the classic nginx footgun).
 #
-# HSTS + HTTP->HTTPS redirect are set at the Cloudflare edge (TLS terminates
-# there), so they are intentionally NOT here.
+# HSTS is set here at the origin (travels through the tunnel to the client) — host-scoped,
+# NO includeSubDomains / preload (the *.bztmon.com wildcard points elsewhere, so forcing HTTPS
+# on every subdomain would be dangerous). HTTP->HTTPS upgrade is handled by Cloudflare.
+add_header Strict-Transport-Security "max-age=31536000" always;
 
 add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self'; connect-src 'self'; worker-src 'self'; manifest-src 'self'; object-src 'none'; base-uri 'self'; form-action 'self'; frame-ancestors 'none'; upgrade-insecure-requests" always;
 add_header X-Content-Type-Options "nosniff" always;