refactor: implement unified border design system

- Define custom border utilities in @layer utilities for consistent theming
- Add border-default (1px gray), border-active (2px primary), border-hover (40% primary), and border-dragging (60% primary) classes
- Update all UI components (Input, Select, TextArea, Button, Dialog, Dropdown) to use unified border classes
- Replace hardcoded border colors (gray-200/300/600/700) with theme-responsive border-border-default
- Update provider cards, MCP components, settings, and forms with new border system
- Remove dark mode border overrides to simplify CSS and improve maintainability
- Ensure all borders automatically adapt to light/dark themes via CSS variables

src/components/ui/button.tsx

@@ -16,7 +16,7 @@ const buttonVariants = cva(
           "bg-red-500 text-white hover:bg-red-600 dark:bg-red-600 dark:hover:bg-red-700",
         // 轮廓按钮
         outline:
-          "border border-gray-200 bg-background hover:bg-gray-100 dark:border-gray-700 dark:hover:bg-gray-800",
+          "border border-border-default bg-background hover:bg-gray-100 hover:border-border-hover dark:hover:bg-gray-800",
         // 次按钮：灰色（对应旧版 secondary）
         secondary:
           "text-gray-500 hover:bg-gray-100 dark:text-gray-400 dark:hover:bg-gray-800 dark:hover:text-gray-200",

src/components/ui/dialog.tsx

@@ -55,7 +55,7 @@ const DialogContent = React.forwardRef<
       <DialogPrimitive.Content
         ref={ref}
         className={cn(
-          "fixed left-1/2 top-1/2 flex flex-col w-full max-w-lg max-h-[90vh] translate-x-[-50%] translate-y-[-50%] border bg-white dark:bg-gray-900 shadow-lg duration-200 data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[state=closed]:slide-out-to-left-1/2 data-[state=closed]:slide-out-to-top-[48%] data-[state=open]:slide-in-from-left-1/2 data-[state=open]:slide-in-from-top-[48%] sm:rounded-lg",
+          "fixed left-1/2 top-1/2 flex flex-col w-full max-w-lg max-h-[90vh] translate-x-[-50%] translate-y-[-50%] border border-border-default bg-white dark:bg-gray-900 shadow-lg duration-200 data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[state=closed]:slide-out-to-left-1/2 data-[state=closed]:slide-out-to-top-[48%] data-[state=open]:slide-in-from-left-1/2 data-[state=open]:slide-in-from-top-[48%] sm:rounded-lg",
           zIndexMap[zIndex],
           className,
         )}

src/components/ui/dropdown-menu.tsx

@@ -40,7 +40,7 @@ const DropdownMenuSubContent = React.forwardRef<
   <DropdownMenuPrimitive.SubContent
     ref={ref}
     className={cn(
-      "z-50 min-w-[8rem] rounded-md border bg-popover p-1 text-popover-foreground shadow-md",
+      "z-50 min-w-[8rem] rounded-md border border-border-default bg-popover p-1 text-popover-foreground shadow-md",
       className,
     )}
     {...props}
@@ -58,7 +58,7 @@ const DropdownMenuContent = React.forwardRef<
       ref={ref}
       sideOffset={sideOffset}
       className={cn(
-        "z-50 min-w-[8rem] overflow-hidden rounded-md border bg-popover p-1 text-popover-foreground shadow-md data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2",
+        "z-50 min-w-[8rem] overflow-hidden rounded-md border border-border-default bg-popover p-1 text-popover-foreground shadow-md data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2",
         className,
       )}
       {...props}

src/components/ui/input.tsx

@@ -9,7 +9,7 @@ const Input = React.forwardRef<HTMLInputElement, InputProps>(
       <input
         type={type}
         className={cn(
-          "flex h-9 w-full rounded-md border border-input bg-background px-3 py-1 text-sm shadow-sm transition-colors file:border-0 file:bg-transparent file:text-sm file:font-medium file:text-foreground placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50",
+          "flex h-9 w-full rounded-md border border-border-default bg-background px-3 py-1 text-sm shadow-sm transition-colors file:border-0 file:bg-transparent file:text-sm file:font-medium file:text-foreground placeholder:text-muted-foreground focus-visible:outline-none focus-visible:border-border-active disabled:cursor-not-allowed disabled:opacity-50",
           className,
         )}
         ref={ref}

src/components/ui/select.tsx

@@ -16,7 +16,7 @@ const SelectTrigger = React.forwardRef<
   <SelectPrimitive.Trigger
     ref={ref}
     className={cn(
-      "flex h-9 w-full items-center justify-between whitespace-nowrap rounded-md border border-input bg-background px-3 py-2 text-sm shadow-sm ring-offset-background placeholder:text-muted-foreground focus:outline-none focus:ring-1 focus:ring-ring disabled:cursor-not-allowed disabled:opacity-50",
+      "flex h-9 w-full items-center justify-between whitespace-nowrap rounded-md border border-border-default bg-background px-3 py-2 text-sm shadow-sm ring-offset-background placeholder:text-muted-foreground focus:outline-none focus:border-border-active disabled:cursor-not-allowed disabled:opacity-50",
       className,
     )}
     {...props}
@@ -37,7 +37,7 @@ const SelectContent = React.forwardRef<
     <SelectPrimitive.Content
       ref={ref}
       className={cn(
-        "relative z-50 min-w-[8rem] overflow-hidden rounded-md border bg-popover text-popover-foreground shadow-md data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2",
+        "relative z-50 min-w-[8rem] overflow-hidden rounded-md border border-border-default bg-popover text-popover-foreground shadow-md data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2",
         className,
       )}
       position={position}

src/components/ui/textarea.tsx

@@ -8,7 +8,7 @@ const Textarea = React.forwardRef<HTMLTextAreaElement, TextareaProps>(
     return (
       <textarea
         className={cn(
-          "flex min-h-[80px] w-full rounded-md border border-input bg-background px-3 py-2 text-sm shadow-sm placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50",
+          "flex min-h-[80px] w-full rounded-md border border-border-default bg-background px-3 py-2 text-sm shadow-sm placeholder:text-muted-foreground focus-visible:outline-none focus-visible:border-border-active disabled:cursor-not-allowed disabled:opacity-50",
           className,
         )}
         ref={ref}