docs: fastpi as external-hardware example, fix stale DietPi-off note
home.md gains the same "external hardware can join the Tailnet and
contribute its own services" framing as the main repo's README/prompt
docs, with fastpi as the example -- the three-machine architecture
(Workstation/Connector/Worker) is unchanged. configuration.md no longer
claims DietPi is switched off; it's been running again since 2026-07-29.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
