ci: run pytest in CI; complete dev requirements; unblock socket test

The suite was never run in CI (only hassfest/HACS), and requirements-dev
listed only pytest + smartthings-local while conftest.py needs the full
Home Assistant test harness.

- requirements-dev.txt: add pytest-homeassistant-custom-component (pulls
  in home-assistant + pytest + pytest-socket) and the integration's
  runtime deps (cbor2, pyOpenSSL, cryptography) needed to import it.
- .github/workflows/validate.yml: add a Pytest job on Python 3.14
  (current Home Assistant's floor) that installs requirements-dev and
  runs the suite.
- test_config_flow.py: the UDP liveness-sweep test needs real loopback
  sockets, which the HA harness blocks by default; take the pytest-socket
  socket_enabled fixture so it runs instead of erroring.

Full suite: 249 passed.

.github/workflows/validate.yml

@@ -35,3 +35,23 @@ jobs:
         uses: hacs/action@main
         with:
           category: integration
+
+  tests:
+    name: Pytest
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.14"
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements-dev.txt
+
+      - name: Run tests
+        run: pytest tests/ -q

requirements-dev.txt

@@ -1,2 +1,11 @@
-pytest>=8.0
+# Test harness — pulls in home-assistant, pytest, and pytest-socket at the
+# matching versions. Current Home Assistant requires Python >= 3.14; pip will
+# resolve the newest home-assistant your interpreter supports.
+pytest-homeassistant-custom-component>=0.13.316
+
+# Integration runtime deps, needed to import the component under test
+# (also declared in custom_components/localthings/manifest.json).
 smartthings-local>=0.1.0
+cbor2>=5.4.6
+pyOpenSSL>=23.0
+cryptography>=41.0

tests/localthings/test_config_flow.py

@@ -67,7 +67,7 @@ def test_order_candidates_prefers_known_ports() -> None:
     assert _order_candidates([49153]) == [49153]
 
 
-def test_find_live_ports_detects_silent_port() -> None:
+def test_find_live_ports_detects_silent_port(socket_enabled) -> None:
     """The UDP liveness sweep flags a bound-but-silent port as live and drops
     ports that refuse with ICMP port-unreachable.
 
@@ -75,6 +75,10 @@ def test_find_live_ports_detects_silent_port() -> None:
     stays silent (open|filtered), like the dishwasher in issue #13 on 49153.
     Two sibling ports are reserved then closed so loopback refuses datagrams
     to them, standing in for the closed ports the scan should discard.
+
+    `socket_enabled` lifts pytest-socket's default block (the HA test harness
+    disables real sockets); this test genuinely needs loopback UDP to exercise
+    the ICMP-unreachable path.
     """
     import socket