design: dark minimal header

app/static/style.css

@@ -38,8 +38,10 @@ body {
   font-size: clamp(1.1rem, 2.2vw, 1.6rem);
 }
 .header-logo {
-  width: 120px;
-  height: auto;
+  height: 28px;
+  width: auto;
+  opacity: 0.9;
+  filter: brightness(0) invert(1);
 }
 .panel {
   background: var(--card);
@@ -86,10 +88,41 @@ button {
   justify-content: space-between;
   align-items: center;
   gap: 1rem;
-  padding: 1rem 1.25rem;
-  background: #fff;
-  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
+  padding: 0.5rem 1.5rem;
+  background: rgba(10, 25, 41, 0.88);
+  backdrop-filter: blur(8px);
+  border-bottom: 1px solid rgba(255,255,255,0.08);
+  position: sticky;
+  top: 0;
+  z-index: 100;
 }
+.header-left { display: flex; align-items: center; }
+.header-right { display: flex; align-items: center; gap: 0.75rem; }
+.header-username {
+  color: rgba(255,255,255,0.55);
+  font-size: 0.8rem;
+  letter-spacing: 0.03em;
+}
+.header-btn {
+  display: inline-flex;
+  align-items: center;
+  padding: 0.3rem 0.9rem;
+  border-radius: 6px;
+  font-size: 0.8rem;
+  font-weight: 500;
+  text-decoration: none;
+  cursor: pointer;
+  border: 1px solid rgba(255,255,255,0.18);
+  background: rgba(255,255,255,0.07);
+  color: rgba(255,255,255,0.8);
+  transition: background 0.15s;
+}
+.header-btn:hover { background: rgba(255,255,255,0.14); }
+.header-btn-logout {
+  border-color: rgba(255,80,80,0.35);
+  color: rgba(255,160,160,0.9);
+}
+.header-btn-logout:hover { background: rgba(255,60,60,0.15); }
 .grid {
   display: grid;
   grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
@@ -714,8 +747,7 @@ button {
   background: linear-gradient(180deg, #a8d2ee 0%, #d8ecf9 100%) !important;
 }
 .dashboard-page .panel,
-.dashboard-page .tile,
-.dashboard-page .header {
+.dashboard-page .tile {
   backdrop-filter: none !important;
   background: rgba(255, 255, 255, 0.9) !important;
   border: 1px solid rgba(198, 218, 235, 0.9) !important;