feat(defects): read API — feed, per-section counts and history (T6)

GET /api/defects returns a newest-first feed joined to the project name,
bounded by limit; ?section=ID narrows to one section's history. GET
/api/defects/counts returns { sectionId: n } for the weak-point map. Adds a
(section_id, created_at) index and a db:seed script; ~2k rows query in ~20ms.

server/api/defects.get.ts

@@ -0,0 +1,12 @@
+import { getDb } from '../db/client'
+import { listDefects } from '../db/repositories/defects'
+
+// Defect feed (F6), newest-first. `?section=ID` narrows to one section's
+// history (the lazy modal load); `?limit=N` bounds the slice.
+export default defineEventHandler(async (event) => {
+  const { section, limit } = getQuery(event)
+  return listDefects(getDb(), {
+    sectionId: typeof section === 'string' ? section : undefined,
+    limit: typeof limit === 'string' ? Number(limit) || undefined : undefined,
+  })
+})