style: improve current provider visual feedback and toast duration

- Add light blue ring border to active provider card instead of solid border
- Fix border flashing issue when switching providers
- Reduce toast notification duration from 4s to 2s for better UX

src/components/providers/ProviderCard.tsx

@@ -94,9 +94,9 @@ export function ProviderCard({
     <div
       className={cn(
         "rounded-lg bg-card p-4 shadow-sm",
-        "transition-[border-color,background-color,box-shadow] duration-200",
+        "transition-[border-color,background-color,box-shadow,ring] duration-200",
         isCurrent
-          ? "border-active border-border-active bg-primary/5"
+          ? "border border-border-default bg-primary/5 ring-2 ring-blue-500/30 dark:ring-blue-400/30"
           : "border border-border-default hover:border-border-hover",
         dragHandleProps?.isDragging &&
           "cursor-grabbing border-active border-border-dragging shadow-lg",

src/components/ui/sonner.tsx

@@ -7,6 +7,7 @@ export function Toaster() {
       richColors
       theme="system"
       toastOptions={{
+        duration: 2000,
         classNames: {
           toast:
             "group rounded-md border bg-background text-foreground shadow-lg",