Build temetro app: dark theme, clinical sidebar, AI chat, settings page

- Linear-inspired dark theme (app/globals.css), forced dark in layout
- Clinical sidebar (components/sidebar-02) with temetro brand
- AI chat UI (components/chat): Cursor-style input, UI-only mock replies
- Settings page (components/settings): Polar-style tabs/sections, UI only
- Route-group app shell: app/(app)/{layout,page,settings}
- shadcn (Base UI) + ai-elements component libraries
- CLAUDE.md: architecture notes + per-folder commit policy

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/components/ai-elements/panel.tsx

@@ -0,0 +1,15 @@
+import { cn } from "@/lib/utils";
+import { Panel as PanelPrimitive } from "@xyflow/react";
+import type { ComponentProps } from "react";
+
+type PanelProps = ComponentProps<typeof PanelPrimitive>;
+
+export const Panel = ({ className, ...props }: PanelProps) => (
+  <PanelPrimitive
+    className={cn(
+      "m-4 overflow-hidden rounded-md border bg-card p-1",
+      className
+    )}
+    {...props}
+  />
+);