fix: replace IP-named dumps with scrubbed named fixtures

Rename tests/fixtures/dumps/{IP}.json to tests/fixtures/{name}_device.json.
Scrub PII: serialNum, otnDUID, modelNum, diagEndPoint replaced with
TEST-* placeholders. conftest: _load_device(name) as primary API;
_load_resources(ip) kept as legacy shim for existing test call sites.

tests/conftest.py

@@ -3,7 +3,7 @@ from pathlib import Path
 
 import pytest
 
-DUMPS = Path(__file__).resolve().parent / 'fixtures' / 'dumps'
+FIXTURES = Path(__file__).resolve().parent / 'fixtures'
 
 
 def _resources_from_dump(dump: dict) -> dict[str, dict]:
@@ -17,16 +17,28 @@ def _resources_from_dump(dump: dict) -> dict[str, dict]:
             if isinstance(v, dict)}
 
 
-def _load_resources(ip: str) -> dict[str, dict]:
-    data = json.loads((DUMPS / f'{ip}.json').read_text())
+def _load_device(name: str) -> dict[str, dict]:
+    data = json.loads((FIXTURES / f'{name}_device.json').read_text())
     return _resources_from_dump(data)
 
 
+def _load_resources(ip: str) -> dict[str, dict]:
+    """Legacy IP-based loader — maps known IPs to named fixtures."""
+    _ip_to_name = {
+        '10.0.0.129': 'dishwasher',
+        '10.0.0.254': 'refrigerator',
+    }
+    name = _ip_to_name.get(ip)
+    if name is None:
+        raise ValueError(f"No fixture for IP {ip!r} — add a scrubbed fixture to tests/fixtures/")
+    return _load_device(name)
+
+
 @pytest.fixture
 def dishwasher_resources() -> dict[str, dict]:
-    return _load_resources('10.0.0.129')
+    return _load_device('dishwasher')
 
 
 @pytest.fixture
 def fridge_resources() -> dict[str, dict]:
-    return _load_resources('10.0.0.254')
+    return _load_device('refrigerator')