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/test_config.py

@@ -21,8 +21,7 @@ class TestDefaultConfig:
 
     def test_default_storage_paths(self):
         config = Config()
-        assert config.storage.devices_file == "data/devices.json"
-        assert config.storage.sync_clocks_file == "data/sync_clocks.json"
+        assert config.storage.database_file == "data/ledgrab.db"
 
     def test_default_mqtt_disabled(self):
         config = Config()
@@ -73,12 +72,11 @@ class TestServerConfig:
 class TestDemoMode:
     def test_demo_rewrites_storage_paths(self):
         config = Config(demo=True)
-        assert config.storage.devices_file.startswith("data/demo/")
-        assert config.storage.sync_clocks_file.startswith("data/demo/")
+        assert config.storage.database_file.startswith("data/demo/")
 
     def test_non_demo_keeps_original_paths(self):
         config = Config(demo=False)
-        assert config.storage.devices_file == "data/devices.json"
+        assert config.storage.database_file == "data/ledgrab.db"
 
 
 class TestGlobalConfig: