feat(ST-qfpqpxzy): DB schema + settings-UI voor min_quota_pct worker-drempel

- User.min_quota_pct Int @default(20) + ClaudeWorker.last_quota_pct/last_quota_check_at
- Migratie add_worker_quota_gate
- lib/schemas/user.ts: minQuotaPctSchema (int, 1-100)
- actions/settings.ts: updateMinQuotaPctAction met auth/demo/zod-guard
- MinQuotaEditor component met numeric input en DemoTooltip
- Settings-pagina: Worker-instellingen sectie

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

prisma/schema.prisma

@@ -121,6 +121,7 @@ model User {
   active_product_id  String?
   active_product     Product?         @relation("UserActiveProduct", fields: [active_product_id], references: [id], onDelete: SetNull)
   idea_code_counter  Int              @default(0)
+  min_quota_pct      Int              @default(20)
   created_at         DateTime         @default(now())
   updated_at         DateTime         @updatedAt
   roles              UserRole[]
@@ -378,9 +379,11 @@ model ClaudeWorker {
   user_id      String
   token        ApiToken @relation(fields: [token_id], references: [id], onDelete: Cascade)
   token_id     String
-  product_id   String?
-  started_at   DateTime @default(now())
-  last_seen_at DateTime @default(now())
+  product_id          String?
+  started_at          DateTime  @default(now())
+  last_seen_at        DateTime  @default(now())
+  last_quota_pct      Int?
+  last_quota_check_at DateTime?
 
   @@unique([token_id])
   @@index([user_id, last_seen_at])