fix(login): remove branding duplication, add shimmer and ping dot (#727)

- Remove redundant SENCHO prefix from kicker (already shown in card header)
- Animate the left accent bar with a slow back-and-forth shimmer sweep
- Replace static status dot with animated ping pulse

frontend/src/index.css

@@ -562,6 +562,10 @@ body {
   from { opacity: 0; transform: scale(0.95); }
   to   { opacity: 1; transform: scale(1); }
 }
+@keyframes shimmer {
+  0%   { transform: translateY(-100%); }
+  100% { transform: translateY(200%); }
+}
 
 /* ─────────────────────────────────────────────────────────────
    ANIMATION UTILITIES
@@ -581,6 +585,9 @@ body {
 .animate-scale-in {
   animation: scale-in var(--duration-fast) var(--ease-spring) both;
 }
+.animate-shimmer {
+  animation: shimmer 4.5s ease-in-out infinite alternate;
+}
 
 /* Stagger delay helpers */
 .animate-delay-50  { animation-delay: 50ms; }