Website: update remediate page for windows users (#43932)

Closes: https://github.com/fleetdm/fleet/issues/39986

Changes:
- Updated the /remediate page to show a different step 1 for Windows
users.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Platform-aware remediation UI: the first remediation step now shows
system-tray instructions and a Windows-specific image for Windows
clients, while non-Windows users continue to see the original menu-bar
instructions and image.
* The page now detects Windows clients and surfaces the appropriate
guidance automatically.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

website/assets/js/pages/microsoft-proxy/remediate.page.js

@@ -3,7 +3,7 @@ parasails.registerPage('remediate', {
   //  ║║║║║ ║ ║╠═╣║    ╚═╗ ║ ╠═╣ ║ ║╣
   //  ╩╝╚╝╩ ╩ ╩╩ ╩╩═╝  ╚═╝ ╩ ╩ ╩ ╩ ╚═╝
   data: {
-    //…
+    isWindowsUser: false,
   },
 
   //  ╦  ╦╔═╗╔═╗╔═╗╦ ╦╔═╗╦  ╔═╗
@@ -13,7 +13,9 @@ parasails.registerPage('remediate', {
     //…
   },
   mounted: async function() {
-    //…
+    if(bowser.windows) {
+      this.isWindowsUser = true;
+    }
   },
 
   //  ╦╔╗╔╔╦╗╔═╗╦═╗╔═╗╔═╗╔╦╗╦╔═╗╔╗╔╔═╗

website/views/pages/microsoft-proxy/remediate.ejs

@@ -5,10 +5,14 @@
       <h1>Secure your device</h1>
       <p>Your organization has blocked sign-in because your computer is failing some security checks. Follow the steps below to restore access.</p>
       <ol purpose="remediation-steps">
-        <li>
+        <li v-if="!isWindowsUser">
           <p>Click the Fleet icon in your menu bar, and select <strong>My device</strong>:</p>
           <img alt="The Fleet Desktop menu" src="/images/remediate-step-1-456x170@2x.png">
         </li>
+        <li v-else>
+          <p>Click the Fleet icon in your system tray to open the <strong>My device</strong> page:</p>
+          <img alt="The Fleet icon in the system tray opening the My device page" src="/images/remediate-step-1-windows-456x170@2x.png">
+        </li>
         <li>
           <p>Navigate to the <strong>Policies</strong> tab:</p>
           <img alt="The Policies tab" src="/images/remediate-step-2-456x170@2x.png">