fix(ST-507): split server-only code helpers into lib/code-server to keep client bundle clean

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/code-server.ts

@@ -0,0 +1,35 @@
+import { prisma } from '@/lib/prisma'
+
+const STORY_AUTO_RE = /^ST-(\d+)$/
+const PBI_AUTO_RE = /^PBI-(\d+)$/
+
+function nextSequential(existing: (string | null)[], pattern: RegExp): number {
+  let max = 0
+  for (const c of existing) {
+    if (!c) continue
+    const m = c.match(pattern)
+    if (m) {
+      const n = Number.parseInt(m[1], 10)
+      if (!Number.isNaN(n) && n > max) max = n
+    }
+  }
+  return max + 1
+}
+
+export async function generateNextStoryCode(productId: string): Promise<string> {
+  const stories = await prisma.story.findMany({
+    where: { product_id: productId },
+    select: { code: true },
+  })
+  const next = nextSequential(stories.map((s) => s.code), STORY_AUTO_RE)
+  return `ST-${String(next).padStart(3, '0')}`
+}
+
+export async function generateNextPbiCode(productId: string): Promise<string> {
+  const pbis = await prisma.pbi.findMany({
+    where: { product_id: productId },
+    select: { code: true },
+  })
+  const next = nextSequential(pbis.map((p) => p.code), PBI_AUTO_RE)
+  return `PBI-${next}`
+}