Move smoke-test.sh to tests/, make it local-only

- Move from rpi/ to tests/ directory
- Add to .gitignore (local tool, not part of distribution)
- Pytest unit tests remain tracked

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -71,6 +71,9 @@ scripts/
 frontends/web/instance/
 frontends/web/certs/
 
+# Integration/smoke tests (local tools)
+tests/smoke-test.sh
+
 # RPi image build artifacts
 *.img
 *.img.xz