fix: remove left/right margins from video player for edge-to-edge display

- Change margin from '0 auto 1rem auto' to '0 0 1rem 0'
- Remove auto left/right margins that were centering the video
- Keep bottom margin for spacing from content below
- Video player now aligns to left edge of card container

src/styles/components/reader.css

@@ -17,7 +17,7 @@
   min-width: 400px;  /* Minimum width */
   max-width: 1000px;   /* Maximum width */
   aspect-ratio: 16/9;
-  margin: 0 auto 1rem auto; /* Center it */
+  margin: 0 0 1rem 0; /* Remove left/right margins, keep bottom margin */
   background: #000;
 }
 .reader.empty { color: #888; }