v0.4+v0.5: TUI dashboard, tab completion, systemd, Docker, process isolation

- New: services/sysmon_widget.py (CPU/MEM/DISK/NET real-time)
- Enhanced: tui_service.py (4-section layout, plugin status panel)
- Enhanced: command_service.py + tui (Tab completion)
- New: deploy/sensu.service (systemd)
- New: deploy/Dockerfile (Alpine, 4200+4240)
- New: services/process_isolated.py (multiprocess plugin isolation)
- Tests: 23/23 passing

deploy/Dockerfile

@@ -0,0 +1,10 @@
+FROM python:3.12-alpine
+WORKDIR /app
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+COPY . .
+RUN mkdir -p data logs
+EXPOSE 4200 4240
+ENV SENSU_ADMIN_PASSWORD=changeme
+ENV SENSU_API_PASSWORD=changeme
+CMD ["python3", "main.py", "--headless"]