Make the home page's AS name search work (closes #151)

The AS Name Search card on the home page said the search was coming
soon. It now asks the new GET /api/v1/search/as?q=<text>, which
searches the AS list built into asinfo, and lists the matches as links
to their AS pages. The answer holds the query, the number of matches
and the first 50 of them; an empty q answers 400. asinfo.Search now
ignores case, uses strings.Contains instead of its own substring loop,
and returns its matches in AS number order. A number, or AS and a
number, typed into the card still opens that AS's page. The card builds
the list with textContent, since the names come from outside data.

Model: opus-5-5

pkg/asinfo/asinfo.go

@@ -2,10 +2,13 @@ package asinfo
 
 import (
 	"bytes"
+	"cmp"
 	"compress/gzip"
 	_ "embed"
 	"encoding/json"
 	"io"
+	"slices"
+	"strings"
 	"sync"
 )
 
@@ -129,36 +132,32 @@ func All() []Info {
 	return result
 }
 
-// Search searches for AS entries where the handle or description contains the query
-// This is a simple case-sensitive substring search
+// Search returns the AS entries whose handle or description contains query,
+// ignoring case, in AS number order. An empty query matches nothing.
 func Search(query string) []Info {
 	once.Do(initRegistry)
 
+	if query == "" {
+		return nil
+	}
+
+	query = strings.ToLower(query)
+
 	defaultRegistry.mu.RLock()
 	defer defaultRegistry.mu.RUnlock()
 
 	var results []Info
 
 	for _, info := range defaultRegistry.byASN {
-		if contains(info.Handle, query) || contains(info.Description, query) {
+		if strings.Contains(strings.ToLower(info.Handle), query) ||
+			strings.Contains(strings.ToLower(info.Description), query) {
 			results = append(results, *info)
 		}
 	}
 
+	slices.SortFunc(results, func(a, b Info) int {
+		return cmp.Compare(a.ASN, b.ASN)
+	})
+
 	return results
 }
-
-// contains is a simple substring search
-func contains(s, substr string) bool {
-	return len(substr) > 0 && len(s) >= len(substr) && containsImpl(s, substr)
-}
-
-func containsImpl(s, substr string) bool {
-	for i := 0; i <= len(s)-len(substr); i++ {
-		if s[i:i+len(substr)] == substr {
-			return true
-		}
-	}
-
-	return false
-}