feat(l1): GET /accounts/me/seats endpoint for seat counter widget

Returns {engineer: SeatCheckResult, l1_tech: SeatCheckResult} for the
authenticated engineer's account. Powers the SeatCounterWidget UI in the
admin/users + account/users surfaces. Engineer+ access only.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/tests/test_invite_seat_enforcement.py

@@ -394,3 +394,64 @@ async def test_role_change_demotion_bypasses_seat_check(client: AsyncClient, tes
     )
     assert resp.status_code == 200, resp.text
     assert resp.json()["account_role"] == "viewer"
+
+
+# ---------------------------------------------------------------------------
+# GET /me/seats — seat counter widget endpoint
+# ---------------------------------------------------------------------------
+
+@pytest.mark.asyncio
+async def test_get_seats_returns_both_role_counts(client: AsyncClient, test_db: AsyncSession):
+    """GET /accounts/me/seats returns engineer + l1_tech seat usage."""
+    owner = await _register(client, email="owner_seats@example.com")
+    account_id = uuid.UUID(owner["account_id"])
+    headers = await _login(client, email="owner_seats@example.com")
+    await _set_sub(test_db, account_id, seat_limit=5, l1_seat_limit=3)
+    # Add 2 engineers and 1 l1_tech as members
+    for i in range(2):
+        await _add_member(test_db, account_id, role="engineer", suffix=f"e{i}")
+    await _add_member(test_db, account_id, role="l1_tech", suffix="l1")
+
+    resp = await client.get("/api/v1/accounts/me/seats", headers=headers)
+    assert resp.status_code == 200, resp.text
+    body = resp.json()
+    assert body["engineer"]["role"] == "engineer"
+    assert body["engineer"]["current"] == 2
+    assert body["engineer"]["limit"] == 5
+    assert body["engineer"]["available"] is True
+    assert body["l1_tech"]["role"] == "l1_tech"
+    assert body["l1_tech"]["current"] == 1
+    assert body["l1_tech"]["limit"] == 3
+    assert body["l1_tech"]["available"] is True
+
+
+@pytest.mark.asyncio
+async def test_get_seats_blocked_for_viewer(client: AsyncClient, test_db: AsyncSession):
+    """GET /accounts/me/seats → 403 for viewer role (engineer+ required)."""
+    from app.core.security import get_password_hash
+
+    # Register an owner for the account
+    owner = await _register(client, email="owner_seats2@example.com")
+    account_id = uuid.UUID(owner["account_id"])
+    await _set_sub(test_db, account_id, seat_limit=5, l1_seat_limit=3)
+
+    # Create a viewer user with a known password directly in the DB
+    viewer_password = "ViewerPass123!"
+    viewer = User(
+        id=uuid.uuid4(),
+        email="viewer_seats@example.com",
+        name="Viewer Seats",
+        account_id=account_id,
+        account_role="viewer",
+        role="engineer",  # system role field (default)
+        is_active=True,
+        password_hash=get_password_hash(viewer_password),
+    )
+    test_db.add(viewer)
+    await test_db.commit()
+
+    # Log in as the viewer
+    viewer_headers = await _login(client, email="viewer_seats@example.com", password=viewer_password)
+
+    resp = await client.get("/api/v1/accounts/me/seats", headers=viewer_headers)
+    assert resp.status_code == 403, resp.text