feat(frontend): deepen single post 1:1 parity with Zibll

Split related style/source settings, add subtitle/meta/allow-view helpers, align cover/author/tags/pay shell markup and CSS with Zibll single.

assets/css/frontend/single-post/cover.css

@@ -211,5 +211,65 @@
 .single-head-cover .cover-meta.single-metabox {
     display: flex; flex-wrap: wrap; gap: 8px 12px; font-size: 12px; color: var(--color-ink-4);
 }
-.aksrt-single-pay-box { margin: 16px 0 20px; }
-.aksrt-single-pay-box .pay-box, .aksrt-single-pay-box .aksrt-paywall { margin: 0; }
+/* Pay box root — Zibll #posts-pay.zib-widget.pay-box */
+#posts-pay.zib-widget,
+#posts-pay.pay-box,
+.aksrt-single-pay-box {
+  margin: 16px 0 20px;
+}
+#posts-pay .aksrt-paywall,
+.aksrt-single-pay-box .pay-box,
+.aksrt-single-pay-box .aksrt-paywall {
+  margin: 0;
+}
+
+/* Cover meta pills + title-h-left */
+.single-cover-con .article-title.title-h-left,
+.single-cover .article-title.title-h-left {
+  color: #fff;
+  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.45);
+  margin: 0;
+}
+.single-metabox.cover-meta,
+.cover-meta.abs-right {
+  position: absolute;
+  top: 12px;
+  right: 12px;
+  z-index: 3;
+  color: #fff;
+}
+.single-metabox .post-metas item,
+.single-metabox .post-metas item a {
+  color: inherit;
+  opacity: 0.92;
+  margin-left: 10px;
+  font-size: 12px;
+}
+.single-metabox .post-metas item .fa,
+.single-metabox .post-metas item i {
+  margin-right: 3px;
+  opacity: 0.9;
+}
+.single-cover-slide-wrap {
+  position: relative;
+  overflow: hidden;
+  border-radius: var(--radius-2xl, 16px);
+}
+.single-cover-slide-wrap .abs-center.left-bottom {
+  z-index: 2;
+  padding: 18px 20px;
+  color: #fff;
+}
+.article-avatar name.flex {
+  gap: 4px;
+  flex-wrap: wrap;
+}
+.article-avatar .aksrt-vip-badge,
+.article-avatar .aksrt-identity-chip {
+  font-size: 12px;
+  line-height: 1.2;
+  vertical-align: middle;
+}
+.article-avatar .display-name {
+  margin-right: 2px;
+}