Add tier-gated RAG and Drive document sources (#42)

Ship allows_rag entitlement (founders/backer/pro/business), enforce it on
document APIs and RAG chat, harden ingest/delete/active lifecycle, and add
Google/Microsoft Drive connect + sync for personal and company knowledge bases.

Closes #43 #44 #45 #46 #47 #48 #49 #50 #51 #52 #53
Parent epic: #42
Related: #11

llm_be/finance/tests/test_plans_quotas.py

@@ -55,6 +55,24 @@ class PlanCatalogTestCase(TestCase):
         self.assertFalse(plans["backer"].is_selectable)
         self.assertTrue(plans["backer"].allows_all_future_features)
 
+    def test_seed_allows_rag_matrix(self):
+        """#43: RAG is gated per-plan — standard is the only tier without it."""
+        plans = {p.slug: p for p in seed_subscription_plans()}
+
+        self.assertTrue(plans["founders"].allows_rag)
+        self.assertFalse(plans["standard"].allows_rag)
+        self.assertTrue(plans["pro"].allows_rag)
+        self.assertTrue(plans["business"].allows_rag)
+        self.assertTrue(plans["backer"].allows_rag)
+
+    def test_allows_feature_recognizes_rag_aliases(self):
+        plans = {p.slug: p for p in seed_subscription_plans()}
+
+        self.assertTrue(plans["pro"].allows_feature("rag"))
+        self.assertTrue(plans["pro"].allows_feature("document_rag"))
+        self.assertFalse(plans["standard"].allows_feature("rag"))
+        self.assertFalse(plans["standard"].allows_feature("document_rag"))
+
 
 class BackerRedeemTestCase(TestCase):
     def setUp(self):
@@ -126,6 +144,23 @@ class QuotaGateTestCase(TestCase):
         )
         assert_feature_allowed(self.user, "image_generation")
 
+    def test_business_allows_rag(self):
+        business = SubscriptionPlan.objects.get(slug="business")
+        assign_plan(self.user, plan=business, source=UserSubscription.Source.ADMIN)
+        assert_feature_allowed(self.user, "rag")
+
+    def test_feature_gate_blocks_rag_on_standard(self):
+        with self.assertRaises(FeatureNotAllowed) as ctx:
+            assert_feature_allowed(self.user, "rag")
+        self.assertEqual(ctx.exception.code, "feature_not_allowed")
+
+    def test_pro_allows_rag(self):
+        pro = SubscriptionPlan.objects.get(slug="pro")
+        assign_plan(
+            self.user, plan=pro, source=UserSubscription.Source.ADMIN
+        )
+        assert_feature_allowed(self.user, "rag")
+
     def test_token_quota_blocks_when_reported(self):
         self.plan.monthly_token_quota = 50
         self.plan.prompt_quota_per_window = 1000