deploy: persistent systemd unit running a pinned release binary with Restart=on-failure + boot enable, plus a liveness timer that restarts the daemon if a register round-trip stops answering

scripts/liveness.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+# echoIRCd liveness probe: do a real NICK/USER register round-trip on the plaintext
+# port and, if the daemon doesn't answer with a 001 welcome, restart it. Catches a
+# hung core (process alive but not serving), which Restart=on-failure alone can't.
+# Run by echoircd-liveness.timer.
+set -u
+PORT="${1:-6767}"
+
+if python3 - "$PORT" <<'PY'
+import socket, sys, time
+port = int(sys.argv[1])
+try:
+    s = socket.create_connection(("127.0.0.1", port), timeout=5)
+    s.settimeout(5)
+    s.sendall(b"NICK livecheck\r\nUSER lc 0 * :liveness\r\n")
+    data = b""
+    end = time.time() + 6
+    while time.time() < end:
+        d = s.recv(4096)
+        if not d:
+            break
+        data += d
+        if b" 001 " in data:
+            break
+    try:
+        s.sendall(b"QUIT :liveness\r\n")
+    except OSError:
+        pass
+    s.close()
+    sys.exit(0 if b" 001 " in data else 1)
+except OSError:
+    sys.exit(1)
+PY
+then
+    exit 0
+fi
+
+echo "echoircd liveness: no 001 from 127.0.0.1:${PORT} within timeout — restarting echoircd-dev.service"
+systemctl restart echoircd-dev.service