fix: update test fixtures for SQLite storage migration

All store tests were passing file paths instead of Database objects
after the JSON-to-SQLite migration. Updated fixtures to create temp
Database instances, rewrote backup e2e tests for binary .db format,
and fixed config tests for the simplified StorageConfig.

server/tests/storage/test_device_store.py

@@ -14,13 +14,16 @@ from wled_controller.storage.device_store import Device, DeviceStore
 
 
 @pytest.fixture
-def temp_storage(tmp_path) -> Path:
-    return tmp_path / "devices.json"
+def tmp_db(tmp_path):
+    from wled_controller.storage.database import Database
+    db = Database(tmp_path / "test.db")
+    yield db
+    db.close()
 
 
 @pytest.fixture
-def store(temp_storage) -> DeviceStore:
-    return DeviceStore(temp_storage)
+def store(tmp_db) -> DeviceStore:
+    return DeviceStore(tmp_db)
 
 
 # ---------------------------------------------------------------------------
@@ -240,23 +243,29 @@ class TestDeviceNameUniqueness:
 
 
 class TestDevicePersistence:
-    def test_persistence_across_instances(self, temp_storage):
-        s1 = DeviceStore(temp_storage)
+    def test_persistence_across_instances(self, tmp_path):
+        from wled_controller.storage.database import Database
+        db = Database(tmp_path / "persist.db")
+        s1 = DeviceStore(db)
         d = s1.create_device(name="Persist", url="http://p", led_count=77)
         did = d.id
 
-        s2 = DeviceStore(temp_storage)
+        s2 = DeviceStore(db)
         loaded = s2.get_device(did)
         assert loaded.name == "Persist"
         assert loaded.led_count == 77
+        db.close()
 
-    def test_update_persists(self, temp_storage):
-        s1 = DeviceStore(temp_storage)
+    def test_update_persists(self, tmp_path):
+        from wled_controller.storage.database import Database
+        db = Database(tmp_path / "persist2.db")
+        s1 = DeviceStore(db)
         d = s1.create_device(name="Before", url="http://x", led_count=10)
         s1.update_device(d.id, name="After")
 
-        s2 = DeviceStore(temp_storage)
+        s2 = DeviceStore(db)
         assert s2.get_device(d.id).name == "After"
+        db.close()
 
 
 # ---------------------------------------------------------------------------
@@ -266,7 +275,9 @@ class TestDevicePersistence:
 
 class TestDeviceThreadSafety:
     def test_concurrent_creates(self, tmp_path):
-        s = DeviceStore(tmp_path / "conc.json")
+        from wled_controller.storage.database import Database
+        db = Database(tmp_path / "conc.db")
+        s = DeviceStore(db)
         errors = []
 
         def _create(i):