feat(branding): add official Mediusa Clinic OS favicon suite, high-resolution OG social card, and update navbar vector logo

public/brand/mediusa-mark.svg

@@ -0,0 +1,28 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <defs>
+    <linearGradient id="medGrad" x1="0%" y1="0%" x2="100%" y2="100%">
+      <stop offset="0%" stop-color="#0a1d3d"/>
+      <stop offset="100%" stop-color="#040915"/>
+    </linearGradient>
+    <filter id="medGlow" x="-20%" y="-20%" width="140%" height="140%">
+      <feDropShadow dx="0" dy="0" stdDeviation="3.5" flood-color="#00b4f8" flood-opacity="0.8"/>
+    </filter>
+  </defs>
+  <!-- Squircle container -->
+  <rect x="7" y="7" width="86" height="86" rx="26" fill="url(#medGrad)" stroke="#00b4f8" stroke-width="5" filter="url(#medGlow)"/>
+  <!-- Hospital Cross Silhouette -->
+  <rect x="42" y="20" width="16" height="60" rx="5" fill="#00b4f8" opacity="0.18"/>
+  <rect x="20" y="42" width="60" height="16" rx="5" fill="#00b4f8" opacity="0.18"/>
+  <!-- Medical Plus Badge -->
+  <rect x="25" y="24" width="14" height="4.5" rx="2" fill="#38bdf8"/>
+  <rect x="29.75" y="19.25" width="4.5" height="14" rx="2" fill="#38bdf8"/>
+  <!-- Bold White M Monogram -->
+  <path d="M 27 73 L 27 43 L 50 61 L 73 43 L 73 73" 
+        fill="none" 
+        stroke="#ffffff" 
+        stroke-width="8" 
+        stroke-linecap="round" 
+        stroke-linejoin="round"/>
+  <!-- Center pulse accent dot -->
+  <circle cx="50" cy="38" r="4.5" fill="#00b4f8" filter="url(#medGlow)"/>
+</svg>