fix(single): fill slide and video cover media like the image cover

Slide-mode images rendered at intrinsic ratio, top-aligned inside the
swiper chain (--pc-height:auto left .swiper-wrapper content-sized), so
the taller box showed a gap at the bottom and never center-cropped like
the image cover. The video cover had the same problem through
video-player.js (height:auto, capped at 70vh).

- aksrt_render_slider scale mode emits --pc-height/--m-height 100% so
  the wrapper/slide/img chain fills the ratio box and object-fit: cover
  center-crops inside it (same pattern as the .scale-height widgets)
- video-player.js renders the video at height:100% + object-fit:cover;
  with an undimensioned container height:100% degrades to auto,
  matching the previous behavior
- drop the dead .single-cover padding-bottom rules (every producer owns
  its height inline, and the rule squeezed the absolutely positioned
  slide inner) and the orphaned --single-cover-scale var in
  tokens.css/compat-vars.css/main.css/InlineStyleBuilder
- rebuild public bundles; extend the single-cover-height contract

assets/css/main.css

@@ -2,7 +2,6 @@ body {
     --mian-max-width: 1200px;
     --posts-card-scale: 70%;
     --posts-list-scale: 70%;
-    --single-cover-scale: 35%;
 
     --theme-color: #f04494;
     --focus-color: var(--theme-color);
@@ -8497,10 +8496,6 @@ body.modal-open .float-btn.wait-pay-btn .hover-show-con {
     margin-left: 50px;
 }
 
-.single-cover {
-    padding-bottom: calc(var(--single-cover-scale) + 50px);
-}
-
 .single-cover-con {
     color: #fff;
     padding: 15px 15px 10px 15px;