Add systemd service and switch app to port 80

Add c2.service unit to run the FastAPI app as workshop-c2. The unit
invokes uv via /usr/bin/env, sets PATH and PYTHONUNBUFFERED, enables
automatic restarts with a short backoff, and logs to the journal using
SyslogIdentifier. Also update main.py's runtime invocation

c2.service

@@ -0,0 +1,28 @@
+[Unit]
+Description=Workshop C2 FastAPI service
+After=network.target
+
+[Service]
+Type=simple
+WorkingDirectory=/home/kemp/ins/teaching/workshop-c-and-c-server
+# Run the requested command. This uses /usr/bin/env to locate `uv` in PATH.
+ExecStart=/usr/bin/env uv run main.py
+# Ensure common system paths are available when using /usr/bin/env
+Environment=PATH=/usr/local/bin:/usr/bin:/bin
+Environment=PYTHONUNBUFFERED=1
+
+# Automatically restart the process if it exits/crashes
+Restart=always
+RestartSec=5
+
+# Log to the journal/syslog with a clear identifier
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=workshop-c2
+
+# (Optional) Uncomment and set a non-root user if desired
+#User=www-data
+#Group=www-data
+
+[Install]
+WantedBy=multi-user.target

main.py

@@ -108,4 +108,4 @@ async def root():
 
 if __name__ == "__main__":
     # Run with: python main.py
-    uvicorn.run("main:app", host="0.0.0.0", port=8000, log_level="info")
+    uvicorn.run("main:app", host="0.0.0.0", port=80, log_level="info")