feat: ST-001–ST-005 foundation — scaffolding, Prisma, schema, seed, env

- ST-001: Next.js 16 + React 19 + TypeScript strict + Tailwind + shadcn/ui + all deps
- ST-002: Prisma v7 setup with better-sqlite3 adapter (local) and pg adapter (cloud)
- ST-003: Full schema migration (users, pbis, stories, sprints, tasks, todos, api_tokens)
- ST-004: Seed with 9 PBIs, ~40 stories, demo user (demo/demo1234), lars user
- ST-005: Zod-validated env vars, .env.example, lib/session, lib/auth, lib/api-auth

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/ui/sonner.tsx

@@ -0,0 +1,49 @@
+"use client"
+
+import { useTheme } from "next-themes"
+import { Toaster as Sonner, type ToasterProps } from "sonner"
+import { CircleCheckIcon, InfoIcon, TriangleAlertIcon, OctagonXIcon, Loader2Icon } from "lucide-react"
+
+const Toaster = ({ ...props }: ToasterProps) => {
+  const { theme = "system" } = useTheme()
+
+  return (
+    <Sonner
+      theme={theme as ToasterProps["theme"]}
+      className="toaster group"
+      icons={{
+        success: (
+          <CircleCheckIcon className="size-4" />
+        ),
+        info: (
+          <InfoIcon className="size-4" />
+        ),
+        warning: (
+          <TriangleAlertIcon className="size-4" />
+        ),
+        error: (
+          <OctagonXIcon className="size-4" />
+        ),
+        loading: (
+          <Loader2Icon className="size-4 animate-spin" />
+        ),
+      }}
+      style={
+        {
+          "--normal-bg": "var(--popover)",
+          "--normal-text": "var(--popover-foreground)",
+          "--normal-border": "var(--border)",
+          "--border-radius": "var(--radius)",
+        } as React.CSSProperties
+      }
+      toastOptions={{
+        classNames: {
+          toast: "cn-toast",
+        },
+      }}
+      {...props}
+    />
+  )
+}
+
+export { Toaster }