Implement AS and prefix detail pages

- Implement handleASDetail() and handlePrefixDetail() HTML handlers
- Create AS detail HTML template with prefix listings
- Create prefix detail HTML template with route information
- Add timeSince template function for human-readable durations
- Update templates.go to include new templates
- Server-side rendered pages as requested (no client-side API calls)

internal/templates/templates.go

@@ -5,14 +5,23 @@ import (
 	_ "embed"
 	"html/template"
 	"sync"
+	"time"
 )
 
 //go:embed status.html
 var statusHTML string
 
+//go:embed as_detail.html
+var asDetailHTML string
+
+//go:embed prefix_detail.html
+var prefixDetailHTML string
+
 // Templates contains all parsed templates
 type Templates struct {
-	Status *template.Template
+	Status       *template.Template
+	ASDetail     *template.Template
+	PrefixDetail *template.Template
 }
 
 var (
@@ -22,17 +31,72 @@ var (
 	once sync.Once
 )
 
+const (
+	hoursPerDay  = 24
+	daysPerMonth = 30
+)
+
+// timeSince returns a human-readable duration since the given time
+func timeSince(t time.Time) string {
+	duration := time.Since(t)
+	if duration < time.Minute {
+		return "just now"
+	}
+	if duration < time.Hour {
+		minutes := int(duration.Minutes())
+		if minutes == 1 {
+			return "1 minute ago"
+		}
+
+		return duration.Truncate(time.Minute).String() + " ago"
+	}
+	if duration < hoursPerDay*time.Hour {
+		hours := int(duration.Hours())
+		if hours == 1 {
+			return "1 hour ago"
+		}
+
+		return duration.Truncate(time.Hour).String() + " ago"
+	}
+	days := int(duration.Hours() / hoursPerDay)
+	if days == 1 {
+		return "1 day ago"
+	}
+	if days < daysPerMonth {
+		return duration.Truncate(hoursPerDay*time.Hour).String() + " ago"
+	}
+
+	return t.Format("2006-01-02")
+}
+
 // initTemplates parses all embedded templates
 func initTemplates() {
 	var err error
 
 	defaultTemplates = &Templates{}
 
+	// Create common template functions
+	funcs := template.FuncMap{
+		"timeSince": timeSince,
+	}
+
 	// Parse status template
 	defaultTemplates.Status, err = template.New("status").Parse(statusHTML)
 	if err != nil {
 		panic("failed to parse status template: " + err.Error())
 	}
+
+	// Parse AS detail template
+	defaultTemplates.ASDetail, err = template.New("asDetail").Funcs(funcs).Parse(asDetailHTML)
+	if err != nil {
+		panic("failed to parse AS detail template: " + err.Error())
+	}
+
+	// Parse prefix detail template
+	defaultTemplates.PrefixDetail, err = template.New("prefixDetail").Funcs(funcs).Parse(prefixDetailHTML)
+	if err != nil {
+		panic("failed to parse prefix detail template: " + err.Error())
+	}
 }
 
 // Get returns the singleton Templates instance
@@ -46,3 +110,13 @@ func Get() *Templates {
 func StatusTemplate() *template.Template {
 	return Get().Status
 }
+
+// ASDetailTemplate returns the parsed AS detail template
+func ASDetailTemplate() *template.Template {
+	return Get().ASDetail
+}
+
+// PrefixDetailTemplate returns the parsed prefix detail template
+func PrefixDetailTemplate() *template.Template {
+	return Get().PrefixDetail
+}