Dashboard UX cleanup: fix German typos, add loading spinner, fix popstate, create static dir

static/dashboard.css

@@ -0,0 +1,92 @@
+:root {
+  --bg: #080c15;
+  --card: rgba(16,19,28,0.65);
+  --text: #f7fafc;
+  --accent: #f97316;
+  --accent-strong: #ff9b3d;
+  --muted: #a8b2c5;
+  --border: rgba(255,255,255,0.08);
+  --surface: rgba(12,15,22,0.75);
+}
+body {
+  margin: 0;
+  font-family: 'Inter', system-ui, -apple-system, sans-serif;
+  background: radial-gradient(circle at 12% 18%, rgba(249,115,22,0.12), transparent 32%), radial-gradient(circle at 78% -6%, rgba(255,153,73,0.12), transparent 32%), linear-gradient(135deg, #070a11 0%, #0b0f18 50%, #080c15 100%);
+  color: var(--text);
+  min-height: 100vh;
+}
+.layout {
+  display: flex;
+  width: 100%;
+  min-height: 100vh;
+  background: radial-gradient(circle at 50% 20%, rgba(255,153,73,0.08), transparent 30%);
+}
+.sidebar {
+  width: 240px;
+  background: linear-gradient(180deg, rgba(12,14,22,0.85), rgba(10,12,18,0.78));
+  border-right: 1px solid rgba(255,255,255,0.06);
+  padding: 24px 20px;
+  box-sizing: border-box;
+  display: flex;
+  flex-direction: column;
+  gap: 18px;
+  backdrop-filter: blur(14px);
+  box-shadow: 8px 0 32px rgba(0,0,0,0.45);
+}
+.brand {
+  font-size: 20px;
+  font-weight: 800;
+  letter-spacing: 0.6px;
+  color: var(--text);
+}
+.nav { display: flex; flex-direction: column; gap: 8px; }
+.nav a {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 11px 13px;
+  border-radius: 14px;
+  color: var(--muted);
+  text-decoration: none;
+  font-weight: 700;
+  transition: background 140ms ease, color 140ms ease, box-shadow 140ms ease, border 140ms ease;
+  border: 1px solid transparent;
+  background: rgba(255,255,255,0.02);
+}
+.nav a .icon { opacity: 0.85; width: 18px; display: inline-flex; justify-content: center; }
+.nav a.active {
+  background: rgba(249,115,22,0.18);
+  color: var(--accent-strong);
+  border-color: rgba(249,115,22,0.45);
+  box-shadow: 0 10px 30px rgba(249,115,22,0.28);
+}
+.nav a:hover {
+  background: rgba(255,255,255,0.06);
+  color: var(--text);
+  border-color: rgba(255,255,255,0.08);
+  box-shadow: 0 8px 22px rgba(0,0,0,0.28);
+}
+.nav a.hidden { display: none; }
+.content {
+  flex: 1;
+  padding: 28px 34px 56px;
+  box-sizing: border-box;
+  background: linear-gradient(145deg, rgba(255,153,73,0.05) 0%, rgba(255,255,255,0) 32%);
+}
+h1 { margin: 0; font-size: 26px; letter-spacing: 0.6px; font-weight: 800; }
+.muted { color: var(--muted); font-size: 13px; }
+main { padding-top: 18px; display: flex; flex-direction: column; gap: 18px; }
+.section { display: none; }
+.section.active { display: block; }
+.section.hidden { display: none !important; }
+.logout {
+  margin-top: auto;
+  border: none;
+  color: white;
+  padding: 10px 12px;
+  border-radius: 12px;
+  cursor: pointer;
+  background: linear-gradient(135deg, #ef4444, #b91c1c);
+  width: 100%;
+  box-shadow: 0 12px 28px rgba(239,68,68,0.32);
+}