feat: consolidate header z-index declarations and ensure sticky positioning hierarchy

Remove duplicate header z-index:100 declaration and consolidate all z-index and positioning overrides into single style block. Maintain sticky positioning hierarchy with header at z-index:100, series summaries at z-index:30 (top:64px), and season dividers at z-index:29 (top:110px).

templates/index.html

@@ -32,6 +32,13 @@ details.series:last-child{margin-bottom:0}
 </style>
 <script>document.querySelectorAll('details.series').forEach(series => { series.open = false; });</script>
 <style>
+header{z-index:100!important}
+#seriesList{overflow:visible!important}
+#seriesList details.series{overflow:visible!important}
+#seriesList details.series>summary{position:sticky!important;top:64px!important;z-index:30!important}
+#seriesList .season-divider td{top:110px!important;z-index:29!important}
+</style>
+<style>
 .subtitle-de{background:#126f39!important;border-color:#19894b!important;color:#d9ffe8!important}
 .col-progress{width:16%}.col-time{width:10%}.col-source{width:10%}.col-language{width:12%}
 .progress-wrap{display:flex;align-items:center;gap:8px}.progress-bar{height:7px;min-width:70px;flex:1;background:#3a3a3a;border-radius:99px;overflow:hidden}.progress-bar span{display:block;height:100%;background:#159447;border-radius:99px}.download-title{color:var(--blue);font-weight:600;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;display:block}
@@ -72,6 +79,7 @@ document.querySelectorAll('details.series').forEach(series=>{const summary=serie
 </script>
 <style>
 .downloading-badge{background:#713c9e!important;border-color:#9257c2!important;color:#f2e5ff!important}.state.downloading{background:#713c9e;color:#f2e5ff}
+header{z-index:100!important}
 .downloading-state{background:#713c9e!important;color:#f2e5ff!important}
 </style>
 <script>