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/services/plans.py

@@ -41,6 +41,7 @@ PLAN_SEED: list[dict[str, Any]] = [
         "is_selectable": True,
         "allows_text_generation": True,
         "allows_image_generation": True,
+        "allows_rag": True,
         "allows_all_future_features": True,
         "prompt_quota_per_window": 300,
         "prompt_window_hours": 6,
@@ -59,6 +60,7 @@ PLAN_SEED: list[dict[str, Any]] = [
         "is_selectable": False,
         "allows_text_generation": True,
         "allows_image_generation": False,
+        "allows_rag": False,
         "allows_all_future_features": False,
         "prompt_quota_per_window": 100,
         "prompt_window_hours": 6,
@@ -70,13 +72,14 @@ PLAN_SEED: list[dict[str, Any]] = [
         "name": "Pro / Creator",
         "description": (
             "Higher message caps and multi-modal workflows for heavy users, "
-            "including image generation when available."
+            "including image generation and Drive/RAG sync when available."
         ),
         "price_cents": 4000,
         "is_public": False,
         "is_selectable": False,
         "allows_text_generation": True,
         "allows_image_generation": True,
+        "allows_rag": True,
         "allows_all_future_features": False,
         "prompt_quota_per_window": 200,
         "prompt_window_hours": 6,
@@ -87,14 +90,16 @@ PLAN_SEED: list[dict[str, Any]] = [
         "slug": SubscriptionPlan.Slug.BUSINESS,
         "name": "Business Team",
         "description": (
-            "Team seats, centralized auth, priority support, and absolute data "
-            "privacy for local companies handling sensitive data."
+            "Team seats, centralized auth, priority support, company Drive/RAG "
+            "sync, and absolute data privacy for local companies handling "
+            "sensitive data."
         ),
         "price_cents": 9900,
         "is_public": False,
         "is_selectable": False,
         "allows_text_generation": True,
         "allows_image_generation": True,
+        "allows_rag": True,
         "allows_all_future_features": False,
         "prompt_quota_per_window": 300,
         "prompt_window_hours": 6,
@@ -113,6 +118,7 @@ PLAN_SEED: list[dict[str, Any]] = [
         "is_selectable": False,
         "allows_text_generation": True,
         "allows_image_generation": True,
+        "allows_rag": True,
         "allows_all_future_features": True,
         "prompt_quota_per_window": 300,
         "prompt_window_hours": 6,
@@ -415,6 +421,7 @@ def plan_to_dict(plan: SubscriptionPlan | None) -> dict[str, Any] | None:
         "features": {
             "text_generation": plan.allows_feature("text_generation"),
             "image_generation": plan.allows_feature("image_generation"),
+            "rag": plan.allows_feature("rag"),
             "all_future_features": plan.allows_all_future_features,
         },
         "prompt_quota_per_window": plan.prompt_quota_per_window,