Docs: expand help and README with params, platform notes; add simple SDFH logo [cai]

assets/sdfh-logo.svg

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="512" height="512" viewBox="0 0 512 512" xmlns="http://www.w3.org/2000/svg" version="1.1">
+  <defs>
+    <linearGradient id="bg" x1="0" y1="0" x2="1" y2="1">
+      <stop offset="0%" stop-color="#0f1a2a"/>
+      <stop offset="100%" stop-color="#1f3a5a"/>
+    </linearGradient>
+    <filter id="glow" x="-50%" y="-50%" width="200%" height="200%">
+      <feGaussianBlur stdDeviation="6" result="blur"/>
+      <feMerge>
+        <feMergeNode in="blur"/>
+        <feMergeNode in="SourceGraphic"/>
+      </feMerge>
+    </filter>
+  </defs>
+  <rect x="0" y="0" width="512" height="512" fill="url(#bg)"/>
+  <g opacity="0.22" fill="none" stroke="#89a7c2" stroke-width="2">
+    <circle cx="256" cy="256" r="180" />
+    <circle cx="256" cy="256" r="140" />
+    <circle cx="256" cy="256" r="100" />
+  </g>
+  <g transform="translate(0,8)" fill="#cfe0f0" opacity="0.18">
+    <path d="M256 120c-44 0-80 36-80 80v24c0 18-10 34-26 42l-14 7c-6 3-10 9-10 16v11c0 7 4 13 10 16l36 16c18 8 38 12 58 12h52c20 0 40-4 58-12l36-16c6-3 10-9 10-16v-11c0-7-4-13-10-16l-14-7c-16-8-26-24-26-42v-24c0-44-36-80-80-80z"/>
+  </g>
+  <g filter="url(#glow)">
+    <text x="50%" y="380" text-anchor="middle" font-family="Trebuchet MS, Segoe UI, sans-serif" font-size="132" font-weight="900" letter-spacing="8" fill="#e8f2fb">SDFH</text>
+  </g>
+</svg>
+
+