Fix Account linking page (#33325)

Fix password form missing whilst linking account even with
`ENABLE_PASSWORD_SIGNIN_FORM = true`.

Remove redundant empty box in account linking sign up page when
`LinkAccountMode` is true.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/user/auth/link_account.tmpl

@@ -16,13 +16,18 @@
 		</div>
 	</overflow-menu>
 	<div class="ui middle very relaxed page grid">
-		<div class="column">
+		<div class="column tw-my-5">
+			{{/* these styles are quite tricky but it needs to be the same as the signin page */}}
 			<div class="ui tab {{if not .user_exists}}active{{end}}" data-tab="auth-link-signup-tab">
+				<div class="tw-flex tw-flex-col tw-gap-4 tw-max-w-2xl tw-m-auto">
 				{{if .AutoRegistrationFailedPrompt}}<div class="ui message">{{.AutoRegistrationFailedPrompt}}</div>{{end}}
 				{{template "user/auth/signup_inner" .}}
+				</div>
 			</div>
 			<div class="ui tab {{if .user_exists}}active{{end}}" data-tab="auth-link-signin-tab">
+				<div class="tw-flex tw-flex-col tw-gap-4 tw-max-w-2xl tw-m-auto">
 				{{template "user/auth/signin_inner" .}}
+				</div>
 			</div>
 		</div>
 	</div>

templates/user/auth/signin.tmpl

@@ -1,6 +1,7 @@
 {{template "base/head" .}}
 <div role="main" aria-label="{{.Title}}" class="page-content user signin{{if .LinkAccountMode}} icon{{end}}">
 	<div class="ui middle very relaxed page grid">
+		{{/* these styles are quite tricky and should also apply to the signup and link_account pages */}}
 		<div class="column tw-flex tw-flex-col tw-gap-4 tw-max-w-2xl tw-m-auto">
 			{{template "user/auth/signin_inner" .}}
 		</div>

templates/user/auth/signup_inner.tmpl

@@ -59,12 +59,12 @@
 </div>
 
 <div class="ui container fluid">
+	{{if not .LinkAccountMode}}
 	<div class="ui attached segment header top tw-flex tw-flex-col tw-items-center">
-		{{if not .LinkAccountMode}}
 		<div class="field">
 			<span>{{ctx.Locale.Tr "auth.already_have_account"}}</span>
 			<a href="{{AppSubUrl}}/user/login">{{ctx.Locale.Tr "auth.sign_in_now"}}</a>
 		</div>
-		{{end}}
 	</div>
+	{{end}}
 </div>