allow clients with no privateKey

see https://github.com/wg-easy/wg-easy/discussions/791

I disabled the download from the frontend.
If someone tries to manually call the API, the privateKey block is set to "REPLACE_ME" to indicate that this value must be set manually.

src/www/css/app.css

@@ -1371,6 +1371,11 @@ video {
   transition-duration: 150ms;
 }
 
+.disabled-link {
+  opacity: 0.25;
+  cursor: default;
+}
+
 .duration-200 {
   transition-duration: 200ms;
 }

src/www/index.html

@@ -258,7 +258,7 @@
                       class="align-middle bg-gray-100 dark:bg-neutral-600 dark:text-neutral-300 p-2 rounded transition"
                       :class="{
                         'hover:bg-red-800 dark:hover:bg-red-800 hover:text-white dark:hover:text-white': client.downloadableConfig,
-                        'inactive': !client.downloadableConfig
+                        'opacity-25': !client.downloadableConfig
                       }"
                       :title="!client.downloadableConfig ? $t('noPrivKey') : $t('showQR')"
                       @click="qrcode = `./api/wireguard/client/${client.id}/qrcode.svg`">
@@ -276,7 +276,7 @@
                       class="align-middle inline-block bg-gray-100 dark:bg-neutral-600 dark:text-neutral-300 p-2 rounded transition"
                       :class="{
                         'hover:bg-red-800 dark:hover:bg-red-800 hover:text-white dark:hover:text-white': client.downloadableConfig,
-                        'inactive': !client.downloadableConfig
+                        'disabled-link': !client.downloadableConfig
                       }"
                       :title="!client.downloadableConfig ? $t('noPrivKey') : $t('downloadConfig')"
                       @click="if(!client.downloadableConfig) { $event.preventDefault(); }">