Fix CSP violations and font 404 from Cloudflare Radar scan

Two conflicting <meta> CSP tags in index.html (plus a separate _headers
policy) meant the browser enforced their intersection, which blocked
the Cloudflare Insights beacon script and its inline bootstrap. k5bss.html
had the same gap in its own CSP. Consolidated to one consistent policy per
surface that allows static.cloudflareinsights.com / cloudflareinsights.com,
and moved index.html's inline script and onerror handler into js/main.js
so script-src no longer needs 'unsafe-inline' there.

Also added the missing fonts/ibm-plex-mono-400.woff2 that style.css has
referenced since it was wired up, which was 404ing.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

_headers

@@ -1,5 +1,5 @@
 /*
-  Content-Security-Policy: default-src 'self'; script-src 'self'; style-src 'self' https://fonts.googleapis.com 'unsafe-inline'; font-src 'self' https://fonts.gstatic.com; img-src 'self' data:; connect-src 'self'; object-src 'none'; base-uri 'none'; frame-ancestors 'none'; form-action 'self'; upgrade-insecure-requests
+  Content-Security-Policy: default-src 'self'; script-src 'self' https://static.cloudflareinsights.com; style-src 'self' https://fonts.googleapis.com 'unsafe-inline'; font-src 'self' https://fonts.gstatic.com; img-src 'self' data:; connect-src 'self' https://cloudflareinsights.com; object-src 'none'; base-uri 'none'; frame-ancestors 'none'; form-action 'self'; upgrade-insecure-requests
   X-Content-Type-Options: nosniff
   X-Frame-Options: DENY
   Referrer-Policy: strict-origin-when-cross-origin