Fix icon and avatar rendering: remove SVG viewport rects + inline avatar styles

- Removed the <rect x='0' y='0' width='24' height='24' fill='none'> viewport
  markers from each social-share SVG. With 'fill=none' the rect was
  still visible if any inherited stroke wasn't suppressed (which turned
  out to be unreliable across themes/CSS specificity).
- Removed redundant width='24' height='24' attributes from each SVG so
  the CSS .project-social-sharing svg { width:20px; height:20px } can
  size them unambiguously.
- Inlined avatar <img> styles (width:50px; height:50px; border-radius:50%;
  object-fit:cover; flex-shrink:0; display:block) so the avatar is
  guaranteed to render as a 50x50 circle regardless of theme CSS.
- Switched .project-owner-avatar to inline-flex so the span shrinks to
  the image's natural size within the flex parent.

assets/css/style.css

@@ -101,7 +101,9 @@
 
 .project-owner-avatar {
     flex: 0 0 auto;
-    display: block;
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
 }
 
 .project-owner-name {