feat(idea): create group auto-generates personas; channel removed; product->product/idea

Per product-idea focus:
- GroupBuilder: 'สินค้า/บริการ/ไอเดีย' label; removed the channel select (channel is now
  chosen at chat time as a scenario, not at persona create). Create now auto-runs analyze
  so personas are generated immediately (no separate Analyze button).
- GroupEdit: analyze button becomes 'สร้างบุคคลต้นแบบเพิ่มเติม' which APPENDS more personas
  (backend analyze?append=true reuses sales kit + keeps existing instead of replacing).
- i18n product label updated.
- User-journey test asserts append adds personas (15->30) and existing kept.
All 9 backend suites pass. Rebuilt dist.

backend/scripts/test_user_journey.py

@@ -85,4 +85,12 @@ for hidden in ("pains","tolerance","negotiation_levers","opener","income","backg
     assert hidden not in pfirst, f"trainee should not see '{hidden}' before chat"
 print("[ok] trainee sees only revealable persona (latent hidden)")
 
+# 11. 'create more personas' = append (does not replace existing ones)
+before = len(C.get(f"/api/groups/{gid}/personas", headers=AH).get_json()["personas"])
+r = C.post(f"/api/groups/{gid}/analyze?append=true", headers=AH)
+assert r.status_code == 200, r.get_json()
+after = len(r.get_json()["personas"])
+assert after > before, f"append should add personas (before={before}, after={after})"
+print(f"[ok] append adds personas ({before} -> {after}); existing kept")
+
 print("ALL USER-JOURNEY FLOW TESTS PASSED")