Change route from wildcard /prefix/* to explicit /prefix/{prefix}/{len}
to properly handle URL-encoded IPv6 addresses with CIDR notation.
- Separate prefix and length into individual path parameters
- Add prefixURL template function for generating correct links
- Remove url.QueryUnescape from handlers (chi handles decoding)
- Add urlEncode template function to properly encode prefix URLs
- Move prefix_length.html to embedded templates with function map
- Prevents broken links for prefixes containing slashes
- Fix GetPrefixDistribution to count unique prefixes using COUNT(DISTINCT prefix) instead of COUNT(*)
- Add /prefixlength/<length> route showing random sample of 500 prefixes
- Make prefix counts on status page clickable links to prefix length pages
- Add GetRandomPrefixesByLength database method
- Create prefix_length.html template with sortable table
- Show prefix age and origin AS with descriptions
