fix(revenue): stop poster modal from blocking the whole revenue page

Two regressions from the previous commit made /user/revenue/ unusable.

The rewrite dropped data-aksrt-affiliate-poster-modal from the modal shell.
That single attribute was both the JS lookup key and the CSS hook, so
initAffiliatePoster() bailed at `if (!button || !modal) return` — which is
why the 推广海报 button never got un-hidden — and no CSS could target the
shell. Restore it.

With the shell back but still visible, main.css's .flex{display:flex} loads
after bootstrap and matches .modal{display:none} on specificity, so the
resting modal rendered as a full-viewport flex box. Combined with .fade's
opacity:0 that is an invisible overlay swallowing every click on the page.
Pin the resting state to display:none and the open state to flex, the same
way credits.css already does for the charge and points-pay modals — that
file documents this exact trap.

Add a contract test asserting the markup, JS selector and CSS hook share
one attribute and that the resting state is explicitly hidden.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

inc/helpers/user-center-renderers/affiliate-poster-modal.php

@@ -19,7 +19,7 @@ if (!empty($GLOBALS['aksrt_affiliate_poster_modal_rendered'])) {
 }
 $GLOBALS['aksrt_affiliate_poster_modal_rendered'] = true;
 ?>
-<div class="modal fade flex jc" id="aksrt-affiliate-poster-modal" tabindex="-1" role="dialog" aria-hidden="true">
+<div class="modal fade flex jc" id="aksrt-affiliate-poster-modal" data-aksrt-affiliate-poster-modal tabindex="-1" role="dialog" aria-hidden="true">
 	<div class="modal-dialog poster-share hover-show" role="document">
 		<div class="modal-content" style="height:220px;overflow:hidden">
 			<div class="poster-imgbox hover-show" data-affiliate-poster-stage></div>