feat: add account management, email verification, AI fixes, and user guides

- Profile settings, account transfer, delete/leave account flows
- Email verification with JWT tokens and Resend integration
- AI assistant/copilot fixes: markdown rendering, shared RAG helpers,
  token tracking, input refocus, model_validate usage
- User guides hub + detail pages with 13 topic guides
- Sidebar and top bar navigation for guides

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

backend/tests/test_account_lifecycle.py

@@ -0,0 +1,109 @@
+"""Tests for leave account and delete account endpoints."""
+
+import pytest
+from httpx import AsyncClient
+
+
+@pytest.mark.asyncio
+class TestLeaveAccount:
+    """Test POST /accounts/me/leave."""
+
+    async def test_leave_as_non_owner(self, client: AsyncClient, test_db):
+        """Non-owner can leave and gets a personal account."""
+        from sqlalchemy import select
+        from app.models.user import User
+
+        # Register owner
+        owner = await client.post("/api/v1/auth/register", json={
+            "email": "owner@example.com", "password": "TestPassword123!", "name": "Owner",
+        })
+        assert owner.status_code == 201
+        owner_data = owner.json()
+
+        # Login as owner
+        login = await client.post("/api/v1/auth/login/json", json={
+            "email": "owner@example.com", "password": "TestPassword123!",
+        })
+        owner_headers = {"Authorization": f"Bearer {login.json()['access_token']}"}
+
+        # Register member
+        member = await client.post("/api/v1/auth/register", json={
+            "email": "member@example.com", "password": "TestPassword123!", "name": "Member",
+        })
+        member_id = member.json()["id"]
+
+        # Move member to owner's account
+        result = await test_db.execute(select(User).where(User.id == member_id))
+        member_user = result.scalar_one()
+        member_user.account_id = owner_data["account_id"]
+        member_user.account_role = "engineer"
+        await test_db.commit()
+
+        # Login as member
+        login = await client.post("/api/v1/auth/login/json", json={
+            "email": "member@example.com", "password": "TestPassword123!",
+        })
+        member_headers = {"Authorization": f"Bearer {login.json()['access_token']}"}
+
+        # Leave
+        response = await client.post("/api/v1/accounts/me/leave", headers=member_headers)
+        assert response.status_code == 200
+
+    async def test_leave_as_owner_fails(self, client: AsyncClient, auth_headers: dict):
+        """Owner cannot leave their own account."""
+        response = await client.post("/api/v1/accounts/me/leave", headers=auth_headers)
+        assert response.status_code == 400
+
+
+@pytest.mark.asyncio
+class TestDeleteAccount:
+    """Test DELETE /accounts/me."""
+
+    async def test_delete_success(self, client: AsyncClient, auth_headers: dict):
+        """Owner with no other members can delete account."""
+        response = await client.request(
+            "DELETE",
+            "/api/v1/accounts/me",
+            json={"current_password": "TestPassword123!"},
+            headers=auth_headers,
+        )
+        assert response.status_code == 200
+
+    async def test_delete_wrong_password(self, client: AsyncClient, auth_headers: dict):
+        """Wrong password returns 401."""
+        response = await client.request(
+            "DELETE",
+            "/api/v1/accounts/me",
+            json={"current_password": "WrongPassword123!"},
+            headers=auth_headers,
+        )
+        assert response.status_code == 401
+
+    async def test_delete_with_members_fails(self, client: AsyncClient, auth_headers: dict, test_db):
+        """Cannot delete account that has other members."""
+        from sqlalchemy import select
+        from app.models.user import User
+
+        # Get owner's account_id
+        me = await client.get("/api/v1/auth/me", headers=auth_headers)
+        account_id = me.json()["account_id"]
+
+        # Register and add member
+        member = await client.post("/api/v1/auth/register", json={
+            "email": "member2@example.com", "password": "TestPassword123!", "name": "Member",
+        })
+        member_id = member.json()["id"]
+
+        result = await test_db.execute(select(User).where(User.id == member_id))
+        member_user = result.scalar_one()
+        member_user.account_id = account_id
+        member_user.account_role = "engineer"
+        await test_db.commit()
+
+        response = await client.request(
+            "DELETE",
+            "/api/v1/accounts/me",
+            json={"current_password": "TestPassword123!"},
+            headers=auth_headers,
+        )
+        assert response.status_code == 400