feat(andreknie.de): improve accessibility and initial loading

privat/CV/andreknie.de/src/index.css

@@ -163,6 +163,34 @@ img {
   color: var(--accent-color);
 }
 
+.page-loading {
+  min-height: 50vh;
+  display: grid;
+  place-items: center;
+  padding: 120px 24px 80px;
+  color: var(--text-secondary);
+}
+
+.sr-only {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  padding: 0;
+  margin: -1px;
+  overflow: hidden;
+  clip: rect(0, 0, 0, 0);
+  white-space: nowrap;
+  border: 0;
+}
+
+button:focus-visible,
+input:focus-visible,
+textarea:focus-visible,
+select:focus-visible {
+  outline: 2px solid var(--accent-color);
+  outline-offset: 3px;
+}
+
 /* Section layout */
 .section-header {
   text-align: center;
@@ -204,3 +232,13 @@ img {
   0% { opacity: 0; }
   100% { opacity: 1; }
 }
+
+@media (prefers-reduced-motion: reduce) {
+  html { scroll-behavior: auto; }
+  *, *::before, *::after {
+    animation-duration: 0.001ms !important;
+    animation-iteration-count: 1 !important;
+    scroll-behavior: auto !important;
+    transition-duration: 0.001ms !important;
+  }
+}