Harden RelayTV integration and prepare HACS 0.4.0 (#2)

* docs: add Home Assistant 0.4.0 hardening roadmap

* fix: protect media credentials and resume state

* feat: authenticate RelayTV API operations

* fix: make targeting and media state reliable

* test: add Home Assistant integration CI

* fix: validate API credentials during setup

* release: prepare HACS 0.4.0

* fix: align pytest dependency pin

* fix: close URL sanitizer gaps and correct player state reporting

Sync the sensitive-query-key list with the RelayTV server (adds auth,
exp, jwt, X-Emby-Token, X-Jellyfin-Token), filter query credentials
from relative URLs instead of returning them verbatim, and preserve
brackets around IPv6 literal hosts.

Also report volume on RelayTV's 0-100 scale unconditionally (a raw 1
is 1%, not full volume) and give the coordinator its own
position_updated_at stamp — the base DataUpdateCoordinator has no
last_update_success_time, so media_position_updated_at silently fell
back to now() on every read and the seek bar never extrapolated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/tests.yml

@@ -0,0 +1,31 @@
+name: Tests
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+
+permissions: {}
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.14"
+          cache: pip
+          cache-dependency-path: requirements_test.txt
+
+      - name: Install test dependencies
+        run: python -m pip install --requirement requirements_test.txt
+
+      - name: Ruff
+        run: ruff check custom_components tests
+
+      - name: Pytest
+        run: python -m pytest -q