Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

docs/public/favicon.svg

@@ -0,0 +1,12 @@
+<svg width="75" height="75" viewBox="0 0 75 75" fill="none" xmlns="http://www.w3.org/2000/svg">
+<rect x="3" y="3" width="69" height="69" rx="10.518" stroke="url(#fav-border)" stroke-width="6"/>
+<rect x="18" y="34" width="39.3661" height="6.56101" fill="url(#fav-dash)"/>
+<defs>
+<linearGradient id="fav-border" x1="-42.9996" y1="124" x2="92.4233" y2="-41.7456" gradientUnits="userSpaceOnUse">
+<stop stop-color="#0F006B"/><stop offset="0.0833" stop-color="#281A81"/><stop offset="0.1667" stop-color="#5D0C83"/><stop offset="0.25" stop-color="#911475"/><stop offset="0.3333" stop-color="#CE2F55"/><stop offset="0.4167" stop-color="#FF6633"/><stop offset="0.5" stop-color="#F6821F"/><stop offset="0.5833" stop-color="#FBAD41"/><stop offset="0.6667" stop-color="#FFCD89"/><stop offset="0.75" stop-color="#FFE9CB"/><stop offset="0.8333" stop-color="#FFF7EC"/><stop offset="0.9167" stop-color="#FFF8EE"/><stop offset="1" stop-color="white"/>
+</linearGradient>
+<linearGradient id="fav-dash" x1="91.4992" y1="27.4982" x2="28.1217" y2="54.1775" gradientUnits="userSpaceOnUse">
+<stop stop-color="white"/><stop offset="0.1293" stop-color="#FFF8EE"/><stop offset="0.6171" stop-color="#FBAD41"/><stop offset="0.848" stop-color="#F6821F"/><stop offset="1" stop-color="#FF6633"/>
+</linearGradient>
+</defs>
+</svg>

docs/public/robots.txt

@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://docs.emdashcms.com/sitemap-index.xml