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

ruff.toml

@@ -0,0 +1,81 @@
+# Lint config for CI.
+#
+# The rule set is broad on purpose and tracks Home Assistant core's conventions
+# reasonably closely, so that this integration would not need a rewrite to be
+# read by anyone used to HA code.
+#
+# CI pins the ruff version (see .gitea/workflows/ci.yml) because ruff's default
+# rule set and formatter output change between releases.
+
+target-version = "py312"
+line-length = 88
+
+# Dated design records. They contain illustrative, intentionally incomplete
+# code blocks and are not maintained source.
+exclude = ["docs"]
+
+[lint]
+select = [
+    "A",     # flake8-builtins
+    "ARG",   # flake8-unused-arguments
+    "ASYNC", # flake8-async
+    "B",     # flake8-bugbear
+    "BLE",   # flake8-blind-except
+    "C4",    # flake8-comprehensions
+    "D",     # pydocstyle
+    "E",     # pycodestyle errors
+    "F",     # pyflakes
+    "FLY",   # flynt
+    "G",     # flake8-logging-format
+    "I",     # isort
+    "ICN",   # flake8-import-conventions
+    "INP",   # flake8-no-pep420
+    "ISC",   # flake8-implicit-str-concat
+    "LOG",   # flake8-logging
+    "N",     # pep8-naming
+    "PERF",  # perflint
+    "PIE",   # flake8-pie
+    "PT",    # flake8-pytest-style
+    "PTH",   # flake8-use-pathlib
+    "Q",     # flake8-quotes
+    "RET",   # flake8-return
+    "RSE",   # flake8-raise
+    "RUF",   # ruff-specific
+    "S",     # flake8-bandit
+    "SIM",   # flake8-simplify
+    "SLF",   # flake8-self
+    "TID",   # flake8-tidy-imports
+    "TRY",   # tryceratops
+    "UP",    # pyupgrade
+    "W",     # pycodestyle warnings
+]
+
+ignore = [
+    # Wants every raise to use a purpose-built exception class whose message is
+    # baked in, rather than `raise DknConnectionError("Request timed out")`.
+    # That trades readable, situation-specific messages for a pile of
+    # single-use classes. Home Assistant core disables this rule too.
+    "TRY003",
+    # Wants `async with asyncio.timeout(...)` at the call site instead of a
+    # `timeout` parameter. The wait helpers here use the timeout value for
+    # scheduling decisions (e.g. refreshing at the halfway point), not just for
+    # cancellation, so the value has to be passed in.
+    "ASYNC109",
+]
+
+[lint.per-file-ignores]
+# Standalone scripts, deliberately not packages, and printing to stdout is
+# their entire job.
+"scripts/*" = ["INP001", "T201"]
+"smoke-test/*" = ["INP001", "T201"]
+
+[lint.isort]
+# Home Assistant core style.
+force-sort-within-sections = true
+combine-as-imports = true
+
+[lint.flake8-tidy-imports]
+ban-relative-imports = "parents"
+
+[lint.pydocstyle]
+convention = "pep257"