feat: restructure into XFlow monorepo with Nuxt 4, Modular Onion Monolith, Android client, and Desktop CLI

apps/web/server/api/groups/[id]/leave.post.ts

@@ -0,0 +1,20 @@
+import { requireAuth } from '~/server/utils/auth'
+import { prisma } from '~/server/utils/prisma'
+
+export default defineEventHandler(async (event) => {
+  const user = requireAuth(event)
+  const groupId = getRouterParam(event, 'id')!
+
+  const group = await prisma.group.findUnique({ where: { id: groupId } })
+  if (!group) throw createError({ statusCode: 404, message: 'Group not found' })
+  if (group.ownerId === user.id) throw createError({ statusCode: 400, message: 'Owner cannot leave group. Delete it instead.' })
+
+  const membership = await prisma.groupMember.findUnique({
+    where: { userId_groupId: { userId: user.id, groupId } }
+  })
+  if (!membership) throw createError({ statusCode: 400, message: 'Not a member' })
+
+  await prisma.groupMember.delete({ where: { id: membership.id } })
+
+  return { success: true, message: `Left group "${group.name}"` }
+})