refactor(types): PEP-604 union sweep + UP007/UP045 enforcement

ruff --select UP007,UP045 --fix converted ~1760 sites across the
backend: `Optional[T]` → `T | None`, `Union[X, Y]` → `X | Y`. The
remaining module-level alias targets that ruff conservatively skips
(BindableFloatInput, ColorList, DeviceConfig) were converted by hand
earlier in the pass. black -formatted the result so the wider unions
fit cleanly under the 100-char line budget.

pyproject.toml now sets [tool.ruff.lint] extend-select = ["UP007",
"UP045"] so future legacy imports fire CI on every push. The
pre-commit ruff hook was bumped from v0.8.0 -> v0.15.12 to recognise
UP045 (split off from UP007 in v0.13).

server/tests/e2e/test_device_flow.py

@@ -5,7 +5,6 @@ create -> get -> update -> brightness -> power -> delete -> verify gone.
 """
 
 
-
 class TestDeviceLifecycle:
     """A user creates a device, inspects it, modifies it, and deletes it."""
 
@@ -76,12 +75,15 @@ class TestDeviceLifecycle:
     def test_create_multiple_devices_and_list(self, client):
         """Creating multiple devices shows all in the list."""
         for i in range(3):
-            resp = client.post("/api/v1/devices", json={
-                "name": f"Device {i}",
-                "url": "mock://test",
-                "device_type": "mock",
-                "led_count": 30,
-            })
+            resp = client.post(
+                "/api/v1/devices",
+                json={
+                    "name": f"Device {i}",
+                    "url": "mock://test",
+                    "device_type": "mock",
+                    "led_count": 30,
+                },
+            )
             assert resp.status_code == 201
 
         resp = client.get("/api/v1/devices")
@@ -108,13 +110,16 @@ class TestDeviceLifecycle:
 
     def test_update_tags(self, client):
         """Tags can be updated independently."""
-        resp = client.post("/api/v1/devices", json={
-            "name": "Tag Device",
-            "url": "mock://test",
-            "device_type": "mock",
-            "led_count": 10,
-            "tags": ["original"],
-        })
+        resp = client.post(
+            "/api/v1/devices",
+            json={
+                "name": "Tag Device",
+                "url": "mock://test",
+                "device_type": "mock",
+                "led_count": 10,
+                "tags": ["original"],
+            },
+        )
         device_id = resp.json()["id"]
 
         resp = client.put(