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_capability.py

@@ -1,5 +1,5 @@
-from custom_components.localthings.ocf.registry.capability import Capability
-from custom_components.localthings.ocf.registry.entities import BinarySensorDesc
+from custom_components.localthings.registry.capability import Capability
+from custom_components.localthings.registry.entities import BinarySensorDesc
 
 
 def test_capability_defaults():