Adds infrastructure/homelab-context.md as the architecture reference for
the cross-client context + MCP + secrets-issuance system. Updates:
- 105-apps.md: two new ## Stacks sections (homelab-mcp, secrets-issuance)
with their deploy pipelines + a row each in the public-hostname table;
changelog entry.
- auto-deploy.md: both new pipelines added to the table (one repo, two
webhooks, same push); per-pipeline notes covering the clone-per-service
pattern and the deploy.sh self-restart caveat; changelog entry.
- README.md: link to the new infrastructure page.
Operational walkthrough already lives at operations/agent-enrollment.md;
this commit is the architecture side of the same story.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
