Add cryptographic security note to System.Random API docs (#12481)

* Initial plan

* Add cryptographic security NOTE to System.Random type-level remarks

Agent-Logs-Url: https://github.com/dotnet/dotnet-api-docs/sessions/864bf564-cbba-4176-b4fa-a901073a6b7c

Co-authored-by: GrabYourPitchforks <1746272+GrabYourPitchforks@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: GrabYourPitchforks <1746272+GrabYourPitchforks@users.noreply.github.com>

Author: Copilot

xml/System/Random.xml

@@ -74,7 +74,14 @@
   </Attributes>
   <Docs>
     <summary>Represents a pseudo-random number generator, which is an algorithm that produces a sequence of numbers that meet certain statistical requirements for randomness.</summary>
-    <remarks>For more information about this API, see <see href="/dotnet/fundamentals/runtime-libraries/system-random">Supplemental API remarks for Random</see>.</remarks>
+    <remarks>
+      <format type="text/markdown"><![CDATA[
+> [!NOTE]
+> To generate a cryptographically secure random number, such as one that's suitable for creating a random password, use one of the static methods in the <xref:System.Security.Cryptography.RandomNumberGenerator> class.
+
+For more information about this API, see [Supplemental API remarks for Random](/dotnet/fundamentals/runtime-libraries/system-random).
+      ]]></format>
+    </remarks>
     <example>
       <format type="text/markdown"><![CDATA[
 The following example creates a single random number generator and calls its <xref:System.Random.NextBytes*>, <xref:System.Random.Next*>, and <xref:System.Random.NextDouble*> methods to generate sequences of random numbers within different ranges.