chore: drop HACS distribution and move CI to Gitea

The GitHub mirror is gone, so the HACS packaging and the GitHub-only CI
no longer have anything to run against.

Remove hacs.json and the .github/ workflow. Both of its jobs (hassfest
and hacs/action) were gated on `github.server_url == 'https://github.com'`
and are GitHub-hosted actions, so neither can run on the Gitea runner.

Replace them with .gitea/workflows/ci.yml:
  - lint: ruff check + ruff format --check, version pinned because ruff's
    default rule set and formatter output move between releases
  - validate: byte-compile, then scripts/validate_integration.py, which
    covers the part of hassfest that matters for a manually installed
    custom component (manifest keys, domain/directory agreement, and
    translations matching strings.json key for key)

README now documents manual installation only, and points at the local
CI commands. manifest.json documentation and issue_tracker point at the
Gitea repo; NOTICE keeps its upstream attribution.

Adopting ruff surfaced two real defects, fixed here:
  - climate.async_set_hvac_mode raised HomeAssistantError for an
    unsupported mode from inside a try that catches Exception, so the
    message was re-wrapped as "Failed to set HVAC mode: Unsupported HVAC
    mode: ...". The validation is now hoisted above the try.
  - config_flow.async_step_reauth_confirm swallowed unexpected exceptions
    into a bare "unknown" error with no log, unlike the user step. It now
    logs via _LOGGER.exception.

Remaining changes are mechanical: import ordering, docstrings on public
methods, ClassVar on mutable class attributes, contextlib.suppress, and
asyncio.TimeoutError -> TimeoutError (an alias since 3.11). The smoke
test now reads the new DknCloudNaClient.socket_connected property rather
than reaching into _socket.

Co-authored-by: anthropic/claude-opus-5

custom_components/dkncloudna/sensor.py

@@ -91,12 +91,14 @@ class DknSensorEntity(DknEntity, SensorEntity):
         mac: str,
         description: DknSensorEntityDescription,
     ) -> None:
+        """Initialise the sensor from its description."""
         super().__init__(coordinator, mac)
         self.entity_description = description
         self._attr_unique_id = f"{DOMAIN}_{mac}_{description.key}"
 
     @property
     def native_value(self) -> Any:
+        """Return the described device value, converted where needed."""
         if self.entity_description.data_key == "work_temp":
             return current_temperature(self._device_data)
         if self.entity_description.data_key == "ext_temp":