fix: pin MCP sidecar versions for stability

- Pin kubernetes-mcp to v0.0.57 (Jan 27, 2025) with token exchange and field selector support
- Pin flux-mcp to v0.41.1 (already pinned)
- Pin homeassistant-mcp to v6.7.1 (Feb 20, 2026) - latest stable release
- Update documentation with version details
- Bump chart version to 0.1.19

This ensures reproducible deployments and prevents unexpected breaking changes
from floating tags (latest/stable).

Generated with Claude Code via Happy

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

README.md

@@ -221,7 +221,7 @@ mcpSidecars:
     enabled: true
     image:
       repository: ghcr.io/homeassistant-ai/ha-mcp
-      tag: stable  # or 'latest' for dev builds
+      tag: v6.7.1  # Override the pinned version if needed
     port: 8087
     resources:
       requests: