fix(home-assistant-mcp): pin appVersion to 7.4.0 (7.4.1 image not published)

Upstream cut a v7.4.1 GitHub release but never published the matching
ghcr.io/homeassistant-ai/ha-mcp:7.4.1 image, so the auto-bumped chart
broke every consumer with ImagePullBackOff. Roll back to 7.4.0 which
is the latest image actually published.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

home-assistant-mcp/Chart.yaml

@@ -2,8 +2,8 @@ apiVersion: v2
 name: home-assistant-mcp
 description: Home Assistant MCP server Helm chart
 type: application
-version: 0.3.0
-appVersion: "7.4.1"
+version: 0.3.1
+appVersion: "7.4.0"
 annotations:
   version-source: github-release:homeassistant-ai/ha-mcp
   version-pattern: "s|^v||"