- Add subnet scanning for printer discovery in Docker environments

- Detect Docker environment automatically via /.dockerenv and cgroup
  - Show subnet input field in Add Printer dialog when running in Docker
  - Scan IP range for Bambu printer ports (8883 MQTT, 990 FTPS)
  - Query SSDP to get printer name/serial/model from discovered IPs
  - Map raw SSDP model codes to friendly names (BL-P001→X1C, O1D→H2D)

backend/tests/integration/test_discovery_api.py

@@ -0,0 +1,144 @@
+"""Integration tests for Discovery API endpoints.
+
+Tests the full request/response cycle for /api/v1/discovery/ endpoints.
+"""
+
+from unittest.mock import AsyncMock, patch
+
+import pytest
+from httpx import AsyncClient
+
+
+class TestDiscoveryAPI:
+    """Integration tests for /api/v1/discovery/ endpoints."""
+
+    # ========================================================================
+    # Info endpoint
+    # ========================================================================
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_get_discovery_info(self, async_client: AsyncClient):
+        """Verify discovery info endpoint returns expected fields."""
+        response = await async_client.get("/api/v1/discovery/info")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "is_docker" in data
+        assert "ssdp_running" in data
+        assert "scan_running" in data
+        assert isinstance(data["is_docker"], bool)
+        assert isinstance(data["ssdp_running"], bool)
+        assert isinstance(data["scan_running"], bool)
+
+    # ========================================================================
+    # SSDP Discovery endpoints
+    # ========================================================================
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_get_discovery_status(self, async_client: AsyncClient):
+        """Verify SSDP discovery status endpoint works."""
+        response = await async_client.get("/api/v1/discovery/status")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "running" in data
+        assert isinstance(data["running"], bool)
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_start_discovery(self, async_client: AsyncClient):
+        """Verify SSDP discovery can be started."""
+        response = await async_client.post("/api/v1/discovery/start?duration=1.0")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "running" in data
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_stop_discovery(self, async_client: AsyncClient):
+        """Verify SSDP discovery can be stopped."""
+        response = await async_client.post("/api/v1/discovery/stop")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "running" in data
+        assert data["running"] is False
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_get_discovered_printers_empty(self, async_client: AsyncClient):
+        """Verify empty list when no printers discovered."""
+        response = await async_client.get("/api/v1/discovery/printers")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert isinstance(data, list)
+
+    # ========================================================================
+    # Subnet scanning endpoints
+    # ========================================================================
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_start_subnet_scan(self, async_client: AsyncClient):
+        """Verify subnet scan can be started."""
+        response = await async_client.post(
+            "/api/v1/discovery/scan",
+            json={"subnet": "192.168.1.0/30", "timeout": 0.1},  # Small subnet for testing
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "running" in data
+        assert "scanned" in data
+        assert "total" in data
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_get_scan_status(self, async_client: AsyncClient):
+        """Verify subnet scan status endpoint works."""
+        response = await async_client.get("/api/v1/discovery/scan/status")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "running" in data
+        assert "scanned" in data
+        assert "total" in data
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_stop_subnet_scan(self, async_client: AsyncClient):
+        """Verify subnet scan can be stopped."""
+        response = await async_client.post("/api/v1/discovery/scan/stop")
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "running" in data
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_subnet_scan_invalid_subnet(self, async_client: AsyncClient):
+        """Verify invalid subnet format is rejected."""
+        response = await async_client.post("/api/v1/discovery/scan", json={"subnet": "invalid-subnet", "timeout": 1.0})
+
+        # Should return 422 validation error or 200 with empty results
+        assert response.status_code in [200, 422]
+
+
+class TestDiscoveryService:
+    """Unit tests for discovery service functionality."""
+
+    @pytest.mark.asyncio
+    @pytest.mark.integration
+    async def test_docker_detection_fields(self, async_client: AsyncClient):
+        """Verify Docker detection returns consistent response."""
+        # Call multiple times to ensure consistency
+        response1 = await async_client.get("/api/v1/discovery/info")
+        response2 = await async_client.get("/api/v1/discovery/info")
+
+        assert response1.status_code == 200
+        assert response2.status_code == 200
+        assert response1.json()["is_docker"] == response2.json()["is_docker"]