Fix prefix length page to show unique prefixes only

- Change GetRandomPrefixesByLength to return unique prefixes instead of all routes
- Use CTE to first select random unique prefixes, then join to get their latest route info
- This ensures each prefix appears only once in the list

internal/database/database.go

@@ -1230,17 +1230,24 @@ func (d *Database) GetPrefixDetails(prefix string) ([]LiveRoute, error) {
 
 // GetRandomPrefixesByLength returns a random sample of prefixes with the specified mask length
 func (d *Database) GetRandomPrefixesByLength(maskLength, ipVersion, limit int) ([]LiveRoute, error) {
+	// Select unique prefixes with their most recent route information
 	query := `
-		SELECT DISTINCT 
-			prefix, mask_length, ip_version, origin_asn, as_path, 
-			peer_ip, last_updated
-		FROM live_routes
-		WHERE mask_length = ? AND ip_version = ?
-		ORDER BY RANDOM()
-		LIMIT ?
+		WITH unique_prefixes AS (
+			SELECT prefix, MAX(last_updated) as max_updated
+			FROM live_routes
+			WHERE mask_length = ? AND ip_version = ?
+			GROUP BY prefix
+			ORDER BY RANDOM()
+			LIMIT ?
+		)
+		SELECT lr.prefix, lr.mask_length, lr.ip_version, lr.origin_asn, lr.as_path, 
+			lr.peer_ip, lr.last_updated
+		FROM live_routes lr
+		INNER JOIN unique_prefixes up ON lr.prefix = up.prefix AND lr.last_updated = up.max_updated
+		WHERE lr.mask_length = ? AND lr.ip_version = ?
 	`
 
-	rows, err := d.db.Query(query, maskLength, ipVersion, limit)
+	rows, err := d.db.Query(query, maskLength, ipVersion, limit, maskLength, ipVersion)
 	if err != nil {
 		return nil, fmt.Errorf("failed to query random prefixes: %w", err)
 	}