chg: usr: improve the gfx on homepage - implement login/register and activation for authentication - and add the first version of profile page #4

assets/css/homepage/_header.scss

@@ -0,0 +1,39 @@
+header {
+    position: relative;
+    width: 100%;
+    overflow: hidden;
+
+    // Minesweeper grid texture
+    background-color: #07090d;
+    background-image:
+        linear-gradient(rgba(35, 111, 135, 0.1) 1px, transparent 1px),
+        linear-gradient(90deg, rgba(35, 111, 135, 0.1) 1px, transparent 1px);
+    background-size: 46px 46px;
+}
+
+// Deep radial vignette – grid fades toward the centre
+header::before {
+    content: '';
+    position: absolute;
+    inset: 0;
+    background: radial-gradient(
+        ellipse 85% 75% at 50% 50%,
+        #07090d 10%,
+        transparent 75%
+    );
+    z-index: 0;
+    pointer-events: none;
+}
+
+// Smoke at the bottom so header bleeds into body
+header::after {
+    content: '';
+    position: absolute;
+    bottom: 0;
+    left: 0;
+    width: 100%;
+    height: 160px;
+    background: linear-gradient(to bottom, transparent, #07090d);
+    z-index: 1;
+    pointer-events: none;
+}