feat(saas): multi-tenant isolation (Phase 1) + rate-limit/audit/org-scoped export (Phase 2)

Phase 1 (tenant isolation):
- g.org_id set on require_auth; assert_tenant()/current_org_id() choke-point helpers.
- Multi-org provisioning: POST /api/admin/users {new_org:true} (super_admin) creates a
  new org + its first admin; GET /api/admin/orgs (super_admin sees all, admin own).
- Fixed latent create_org double-id bug (dict id != store key).
- test_saas_tenant.py: org2 admin blocked from org1 group (403), can't list org1
  groups/users, sees only own org; super_admin sees all.

Phase 2 (hardening):
- Rate limit login (per-IP + per-username) + chat send (per-user) to protect LLM cost
  and slow brute force; services/rate_limit.py (in-memory + disk, no external deps).
- Audit log data/audit/audit.jsonl on org.create, user.promote_super_admin, analytics.export.
- CSV export now org-scoped (admin exports only own org).
All 8 backend suites pass.

backend/scripts/test_saas_tenant.py

@@ -0,0 +1,83 @@
+"""Test: SaaS multi-tenant isolation + hardening basics."""
+import os, sys, tempfile, warnings
+from pathlib import Path
+
+warnings.filterwarnings("ignore")
+BACKEND = str(Path(__file__).resolve().parents[1])
+sys.path.insert(0, BACKEND)
+
+from app.factory import create_app
+from app.config import Config
+
+td = tempfile.mkdtemp()
+Config.DATA_DIR = Path(td)
+sys.path.insert(0, BACKEND + "/scripts")
+from mock_llm import MockLLM
+
+app = create_app()
+app.extensions["llm"] = MockLLM()
+C = app.test_client()
+
+def tok(u, p): return C.post("/api/auth/login", json={"username": u, "password": p}).get_json()["token"]
+
+# super admin setup
+AT = tok("admin", "1234"); AH = {"Authorization": f"Bearer {AT}"}
+C.post("/api/auth/setup", headers=AH, json={"username": "admin", "email": "a@b.co", "password": "newpass"})
+AT = tok("admin", "newpass"); AH = {"Authorization": f"Bearer {AT}"}
+
+# create org1 data (a group)
+gid = C.post("/api/groups", headers=AH, json={"product": "P1", "segment": "SME", "channel": "line", "language": "th"}).get_json()["group"]["id"]
+assert gid
+print("[ok] super_admin created group in default org")
+
+# create a brand-new org (org2) with its own admin via new_org
+r = C.post("/api/admin/users", headers=AH, json={
+    "username": "adm2", "name": "Org2 Admin", "password": "pppp", "role": "admin", "new_org": True
+})
+assert r.status_code == 201, r.get_json()
+org2_id = r.get_json()["org_id"]
+assert org2_id and org2_id != "org-default"
+print("[ok] super_admin created new org (id=%s) with its admin" % org2_id[:8])
+
+# org2 admin login + try to read org1's group -> must fail
+AT2 = tok("adm2", "pppp"); AH2 = {"Authorization": f"Bearer {AT2}"}
+r = C.get(f"/api/groups/{gid}", headers=AH2)
+assert r.status_code == 403, ("org2 admin should NOT read org1 group", r.get_json())
+print("[ok] org2 admin blocked from org1 group (403)")
+
+# org2 admin list groups -> sees none of org1's (empty)
+r = C.get("/api/groups", headers=AH2)
+assert r.status_code == 200
+groups = r.get_json()["groups"]
+assert all(g.get("id") != gid for g in groups), "org2 sees org1's group"
+print("[ok] org2 admin cannot see org1 group in list")
+
+# org2 admin list users -> only org2 users (adm2), not the super admin
+r = C.get("/api/admin/users", headers=AH2)
+names = [u.get("username") for u in r.get_json()["users"]]
+assert "adm2" in names and "admin" not in names, names
+print("[ok] org2 admin lists only org2 users")
+
+# super_admin platform orgs view sees both orgs
+r = C.get("/api/admin/orgs", headers=AH)
+orgs = r.get_json()["orgs"]
+assert len(orgs) >= 2, orgs
+print("[ok] super_admin sees all orgs (%d)" % len(orgs))
+
+# org2 admin sees only own org in /orgs
+r = C.get("/api/admin/orgs", headers=AH2)
+orgs = r.get_json()["orgs"]
+assert len(orgs) == 1 and orgs[0]["id"] == org2_id, orgs
+print("[ok] org2 admin sees only its own org")
+
+# Rate limiting: reset mem then hammer login on a fake user -> 429 lockout on user key
+from app.services import rate_limit
+rate_limit._mem.clear()
+code = None
+for _ in range(11):
+    code = C.post("/api/auth/login", json={"username": "nobody", "password": "x"}).status_code
+assert code == 429, ("expected 429 after login hammering", code)
+rate_limit._mem.clear()
+print("[ok] login rate-limit returns 429 after abuse")
+
+print("ALL SAAS MULTI-TENANT TESTS PASSED")