Refactor backend to support interface-definition driven model resources

- Introduce a new model structure for managing interface definitions and model resources, enhancing the backend's capability to handle various service integrations.
- Update the Makefile to reflect changes in database seeding and resource management commands.
- Remove the deprecated credentials management routes and replace them with a unified model registry API.
- Modify existing routes and schemas to align with the new model structure, ensuring seamless integration with the frontend.
- Enhance database seeding scripts to populate new model resources and their configurations.
- Update README documentation to reflect the new architecture and usage instructions for model resources and interface definitions.

frontend/src/components/ui/page-header.tsx

@@ -0,0 +1,39 @@
+import type { ReactNode } from "react";
+
+import { cn } from "@/lib/utils";
+
+export type PageHeaderProps = {
+  title: string;
+  description?: ReactNode;
+  /** 右侧主操作(如「创建助手」按钮) */
+  action?: ReactNode;
+  className?: string;
+};
+
+/** 列表/资源页统一页头:标题 + 说明 + 右侧操作,移动端纵向堆叠 */
+export function PageHeader({
+  title,
+  description,
+  action,
+  className,
+}: PageHeaderProps) {
+  return (
+    <div
+      className={cn(
+        "flex flex-col items-start justify-between gap-5 sm:flex-row sm:gap-6",
+        className,
+      )}
+    >
+      <div>
+        <h1 className="font-display display-lg text-ink">{title}</h1>
+        {description && (
+          <p className="mt-3 max-w-2xl text-[15px] leading-7 text-muted-foreground">
+            {description}
+          </p>
+        )}
+      </div>
+
+      {action && <div className="w-full shrink-0 sm:w-auto">{action}</div>}
+    </div>
+  );
+}