feat: show message if signups are disabled

locales/en-US.yml

@@ -1074,6 +1074,8 @@ customKaTeXMacroDescription: "Set up macros to write mathematical expressions ea
   \ supported; advanced syntax, such as conditional branching, cannot be used here."
 enableCustomKaTeXMacro: "Enable custom KaTeX macros"
 noteId: "Post ID"
+signupsDisabled: "Signups on this server are currently disabled, but you can always sign up at another server! If you have an invitation code for this server, please enter it below."
+findOtherInstance: "Find another server"
 
 _sensitiveMediaDetection:
   description: "Reduces the effort of server moderation through automatically recognizing\

packages/client/src/components/MkSignup.vue

@@ -4,6 +4,10 @@
 		autocomplete="new-password"
 		@submit.prevent="onSubmit"
 	>
+		<p>{{ i18n.ts.signupsDisabled }}</p>
+		<MkButton rounded gradate link to="https://calckey.org/join"
+			>{{ i18n.ts.findOtherInstance }}
+		</MkButton>
 		<MkInput
 			v-if="instance.disableRegistration"
 			v-model="invitationCode"