feat: update all endpoints and schemas for account-based model

Replace team_id with account_id across all API endpoints (trees,
categories, tags, steps, step_categories, admin, auth). Add new
accounts and webhooks endpoints. Registration now atomically creates
Account + Subscription, with account_invite_code bypassing the
platform invite gate.

Schemas updated for account_id/account_role. 82 tests passing
including 18 new tests for accounts, subscriptions, and permissions.

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

backend/tests/test_subscription_limits.py

@@ -0,0 +1,129 @@
+"""Integration tests for subscription limits."""
+
+import pytest
+from httpx import AsyncClient
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+
+class TestSubscriptionLimits:
+    """Test suite for subscription plan limits."""
+
+    @pytest.mark.asyncio
+    async def test_free_plan_tree_limit(self, client: AsyncClient, auth_headers: dict):
+        """Test that free plan has tree creation limit of 3."""
+        tree_template = {
+            "name": "Limit Test Tree",
+            "tree_structure": {
+                "id": "root",
+                "type": "solution",
+                "title": "Test",
+                "description": "Test tree"
+            }
+        }
+
+        # Create trees up to the limit
+        for i in range(3):
+            tree_data = {**tree_template, "name": f"Tree {i+1}"}
+            response = await client.post("/api/v1/trees", json=tree_data, headers=auth_headers)
+            assert response.status_code == 201, f"Failed creating tree {i+1}: {response.json()}"
+
+        # 4th tree should fail with 402
+        tree_data = {**tree_template, "name": "Tree 4 Over Limit"}
+        response = await client.post("/api/v1/trees", json=tree_data, headers=auth_headers)
+        assert response.status_code == 402
+        assert "limit" in response.json()["detail"].lower()
+
+    @pytest.mark.asyncio
+    async def test_subscription_details_show_usage(self, client: AsyncClient, auth_headers: dict):
+        """Test that subscription details reflect actual usage."""
+        # Check initial usage
+        response = await client.get("/api/v1/accounts/me/subscription", headers=auth_headers)
+        assert response.status_code == 200
+        initial_usage = response.json()["usage"]
+        assert initial_usage["tree_count"] == 0
+
+        # Create a tree
+        tree_data = {
+            "name": "Usage Test Tree",
+            "tree_structure": {
+                "id": "root",
+                "type": "solution",
+                "title": "Test",
+                "description": "Test"
+            }
+        }
+        create_resp = await client.post("/api/v1/trees", json=tree_data, headers=auth_headers)
+        assert create_resp.status_code == 201
+
+        # Check usage increased
+        response = await client.get("/api/v1/accounts/me/subscription", headers=auth_headers)
+        assert response.status_code == 200
+        updated_usage = response.json()["usage"]
+        assert updated_usage["tree_count"] == 1
+
+    @pytest.mark.asyncio
+    async def test_super_admin_bypasses_limits(
+        self, client: AsyncClient, admin_auth_headers: dict
+    ):
+        """Test that super admin can create trees without limit checks."""
+        tree_template = {
+            "name": "Admin Tree",
+            "tree_structure": {
+                "id": "root",
+                "type": "solution",
+                "title": "Test",
+                "description": "Test tree"
+            },
+            "is_default": True  # Default trees skip limit check
+        }
+
+        # Super admin creating default trees should always work
+        for i in range(5):
+            tree_data = {**tree_template, "name": f"Admin Tree {i+1}"}
+            response = await client.post(
+                "/api/v1/trees", json=tree_data, headers=admin_auth_headers
+            )
+            assert response.status_code == 201
+
+    @pytest.mark.asyncio
+    async def test_free_plan_limits_correct(self, client: AsyncClient, auth_headers: dict):
+        """Test that free plan limits are correct."""
+        response = await client.get("/api/v1/accounts/me/subscription", headers=auth_headers)
+        assert response.status_code == 200
+        limits = response.json()["limits"]
+        assert limits["plan"] == "free"
+        assert limits["max_trees"] == 3
+        assert limits["max_sessions_per_month"] == 20
+        assert limits["max_users"] == 1
+        assert limits["custom_branding"] is False
+        assert limits["priority_support"] is False
+
+    @pytest.mark.asyncio
+    async def test_upgraded_plan_has_higher_limits(
+        self, client: AsyncClient, auth_headers: dict, test_db: AsyncSession
+    ):
+        """Test that upgrading plan increases limits."""
+        from app.models.subscription import Subscription
+        from app.models.user import User
+
+        # Get the user's subscription and upgrade it
+        me_resp = await client.get("/api/v1/auth/me", headers=auth_headers)
+        account_id_str = me_resp.json()["account_id"]
+
+        from uuid import UUID
+        account_id = UUID(account_id_str)
+        result = await test_db.execute(
+            select(Subscription).where(Subscription.account_id == account_id)
+        )
+        sub = result.scalar_one()
+        sub.plan = "pro"
+        await test_db.commit()
+
+        # Check limits are now pro
+        response = await client.get("/api/v1/accounts/me/subscription", headers=auth_headers)
+        assert response.status_code == 200
+        limits = response.json()["limits"]
+        assert limits["plan"] == "pro"
+        assert limits["max_trees"] == 25
+        assert limits["max_sessions_per_month"] == 200