CI: auto-release on manifest version bump; validate on PR/push

Adds .github/workflows/release.yml (for HA integrations, watches
custom_components/<domain>/manifest.json; for ha-adb-common, watches
pyproject.toml). When the version field changes on main, the workflow
creates a matching v<version> tag and a GitHub Release with
auto-generated notes — as long as the tag doesn't already exist.

For the four HA integrations, also adds validate.yml running HACS's
official validator and Home Assistant's hassfest against every PR,
push to main, and nightly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/validate.yml

@@ -0,0 +1,26 @@
+name: Validate
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  schedule:
+    - cron: "0 6 * * *"
+  workflow_dispatch:
+
+jobs:
+  hacs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: HACS validation
+        uses: hacs/action@main
+        with:
+          category: integration
+
+  hassfest:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Hassfest validation
+        uses: home-assistant/actions/hassfest@master