Rename ocf/ to registry/, it's a capability registry now

The DTLS/CoAP transport code that made "ocf" an accurate name moved out to
the smartthings-local package. What's left here (capability.py, entities.py,
discovery.py, adapter.py, identity.py, capabilities/, by_type/, plus the
/device/0 batch parser) is entirely the device capability registry, so name
the package for what it does.

Flattened the redundant ocf/registry/ nesting into a single top-level
registry/ package and updated every import across the platform modules and
test suite accordingly. Verified: full test suite (80/80) passes, and the
Docker dev container reconnects to both live appliances and rediscovers
their entities cleanly after the rename.

tests/test_fridge_multi_instance.py

@@ -7,9 +7,9 @@ pattern capability that auto-derives distinct keys from the href segments.
 """
 from tests.conftest import _load_resources
 
-from custom_components.localthings.ocf.registry.adapter import _key
-from custom_components.localthings.ocf.registry.by_type import refrigerator
-from custom_components.localthings.ocf.registry.discovery import discover
+from custom_components.localthings.registry.adapter import _key
+from custom_components.localthings.registry.by_type import refrigerator
+from custom_components.localthings.registry.discovery import discover
 
 
 def test_two_doors_get_distinct_keys():