feat(ST-351): add UserAvatar component and /api/users/[id]/avatar route

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

app/api/users/[id]/avatar/route.ts

@@ -0,0 +1,28 @@
+import { prisma } from '@/lib/prisma'
+import { requireUser } from '@/lib/auth'
+
+export async function GET(_request: Request, { params }: { params: Promise<{ id: string }> }) {
+  try {
+    await requireUser()
+  } catch {
+    return new Response(null, { status: 401 })
+  }
+
+  const { id } = await params
+
+  const user = await prisma.user.findUnique({
+    where: { id },
+    select: { avatar_data: true },
+  })
+
+  if (!user?.avatar_data) {
+    return new Response(null, { status: 404 })
+  }
+
+  return new Response(user.avatar_data, {
+    headers: {
+      'Content-Type': 'image/webp',
+      'Cache-Control': 'private, max-age=3600',
+    },
+  })
+}

components/shared/user-avatar.tsx

@@ -0,0 +1,33 @@
+'use client'
+
+import { Avatar, AvatarFallback, AvatarImage } from '@/components/ui/avatar'
+import { cn } from '@/lib/utils'
+
+type AvatarSize = 'xs' | 'sm' | 'md' | 'lg'
+
+const SIZE_CLASSES: Record<AvatarSize, string> = {
+  xs: 'size-6 text-[10px]',
+  sm: 'size-8 text-xs',
+  md: 'size-10 text-sm',
+  lg: 'size-12 text-base',
+}
+
+interface UserAvatarProps {
+  userId: string
+  username: string
+  size?: AvatarSize
+  className?: string
+}
+
+export function UserAvatar({ userId, username, size = 'md', className }: UserAvatarProps) {
+  const initials = username.slice(0, 2).toUpperCase()
+
+  return (
+    <Avatar className={cn(SIZE_CLASSES[size], className)}>
+      <AvatarImage src={`/api/users/${userId}/avatar`} alt={username} />
+      <AvatarFallback className="bg-primary-container text-primary-container-foreground font-medium">
+        {initials}
+      </AvatarFallback>
+    </Avatar>
+  )
+}

components/ui/avatar.tsx

@@ -0,0 +1,109 @@
+"use client"
+
+import * as React from "react"
+import { Avatar as AvatarPrimitive } from "@base-ui/react/avatar"
+
+import { cn } from "@/lib/utils"
+
+function Avatar({
+  className,
+  size = "default",
+  ...props
+}: AvatarPrimitive.Root.Props & {
+  size?: "default" | "sm" | "lg"
+}) {
+  return (
+    <AvatarPrimitive.Root
+      data-slot="avatar"
+      data-size={size}
+      className={cn(
+        "group/avatar relative flex size-8 shrink-0 rounded-full select-none after:absolute after:inset-0 after:rounded-full after:border after:border-border after:mix-blend-darken data-[size=lg]:size-10 data-[size=sm]:size-6 dark:after:mix-blend-lighten",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function AvatarImage({ className, ...props }: AvatarPrimitive.Image.Props) {
+  return (
+    <AvatarPrimitive.Image
+      data-slot="avatar-image"
+      className={cn(
+        "aspect-square size-full rounded-full object-cover",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function AvatarFallback({
+  className,
+  ...props
+}: AvatarPrimitive.Fallback.Props) {
+  return (
+    <AvatarPrimitive.Fallback
+      data-slot="avatar-fallback"
+      className={cn(
+        "flex size-full items-center justify-center rounded-full bg-muted text-sm text-muted-foreground group-data-[size=sm]/avatar:text-xs",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function AvatarBadge({ className, ...props }: React.ComponentProps<"span">) {
+  return (
+    <span
+      data-slot="avatar-badge"
+      className={cn(
+        "absolute right-0 bottom-0 z-10 inline-flex items-center justify-center rounded-full bg-primary text-primary-foreground bg-blend-color ring-2 ring-background select-none",
+        "group-data-[size=sm]/avatar:size-2 group-data-[size=sm]/avatar:[&>svg]:hidden",
+        "group-data-[size=default]/avatar:size-2.5 group-data-[size=default]/avatar:[&>svg]:size-2",
+        "group-data-[size=lg]/avatar:size-3 group-data-[size=lg]/avatar:[&>svg]:size-2",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function AvatarGroup({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="avatar-group"
+      className={cn(
+        "group/avatar-group flex -space-x-2 *:data-[slot=avatar]:ring-2 *:data-[slot=avatar]:ring-background",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function AvatarGroupCount({
+  className,
+  ...props
+}: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="avatar-group-count"
+      className={cn(
+        "relative flex size-8 shrink-0 items-center justify-center rounded-full bg-muted text-sm text-muted-foreground ring-2 ring-background group-has-data-[size=lg]/avatar-group:size-10 group-has-data-[size=sm]/avatar-group:size-6 [&>svg]:size-4 group-has-data-[size=lg]/avatar-group:[&>svg]:size-5 group-has-data-[size=sm]/avatar-group:[&>svg]:size-3",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+export {
+  Avatar,
+  AvatarImage,
+  AvatarFallback,
+  AvatarGroup,
+  AvatarGroupCount,
+  AvatarBadge,
+}