feat: add UDP syslog receiver for network device log collection

scripts/syslog_receiver.py: asyncio UDP server listening on port 5140,
appends raw syslog lines to network-syslog.txt for the Turnstone live
watcher to tail. Requires no root — port 5140 is non-privileged.

scripts/turnstone-syslog-receiver.service: systemd unit for auto-start.

app/ingest/syslog.py: strip optional RFC 3164 <PRI> prefix before
parsing so network-forwarded syslog (OpenWRT logd, Arista EOS, etc.)
is handled correctly without the PRI value breaking the regex.

app/ingest/syslog.py

@@ -26,6 +26,8 @@ _MONTHS = {
 
 # May 11 14:23:01 hostname ident[pid]: message
 # May  1 04:00:00 hostname ident: message   (no pid, day may be space-padded)
+# <134>May 11 14:23:01 ...                  (optional RFC 3164 PRI prefix from network syslog)
+_PRI_RE = re.compile(r"^<\d{1,3}>")
 _LINE_RE = re.compile(
     r"^(?P<month>Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)"
     r"\s+(?P<day>\d{1,2})\s+(?P<time>\d{2}:\d{2}:\d{2})"
@@ -35,7 +37,8 @@ _LINE_RE = re.compile(
 
 
 def is_syslog(first_line: str) -> bool:
-    return bool(_LINE_RE.match(first_line.strip()))
+    stripped = _PRI_RE.sub("", first_line.strip(), count=1)
+    return bool(_LINE_RE.match(stripped))
 
 
 def _parse_ts(month_str: str, day: str, time_str: str) -> tuple[str, str]:
@@ -80,7 +83,7 @@ def parse(
         )
 
     for raw_line in lines:
-        line = raw_line.rstrip("\n")
+        line = _PRI_RE.sub("", raw_line.rstrip("\n"), count=1)
         m = _LINE_RE.match(line)
         if m:
             if pending_text is not None:

scripts/syslog_receiver.py

@@ -0,0 +1,96 @@
+#!/usr/bin/env python3
+"""UDP syslog receiver for Turnstone cluster monitoring.
+
+Listens on UDP port 5140 (non-privileged) and appends received messages
+to /devl/turnstone-cluster/data/network-syslog.txt for the Turnstone
+live watcher to tail.
+
+Each line written is:
+  <source_ip> <raw_syslog_message>
+
+This preserves the original syslog content while adding the sender IP so
+Turnstone's syslog ingestor can tag entries by device.
+
+Usage:
+  python3 syslog_receiver.py [--port 5140] [--output /path/to/network-syslog.txt]
+
+Installed as: turnstone-syslog-receiver.service (see adjacent .service file)
+"""
+from __future__ import annotations
+
+import argparse
+import asyncio
+import logging
+import signal
+import sys
+from pathlib import Path
+
+logger = logging.getLogger("syslog-receiver")
+
+DEFAULT_PORT = 5140
+DEFAULT_OUTPUT = "/devl/turnstone-cluster/data/network-syslog.txt"
+
+
+class SyslogReceiverProtocol(asyncio.DatagramProtocol):
+    def __init__(self, output_path: Path) -> None:
+        self._output_path = output_path
+        self._fh = output_path.open("a", buffering=1)  # line-buffered
+
+    def datagram_received(self, data: bytes, addr: tuple[str, int]) -> None:
+        try:
+            message = data.decode("utf-8", errors="replace").rstrip("\r\n")
+        except Exception:
+            return
+        if not message:
+            return
+        # RFC 3164 messages already include the sending hostname — write raw.
+        try:
+            self._fh.write(f"{message}\n")
+        except OSError as exc:
+            logger.error("Write failed: %s", exc)
+
+    def error_received(self, exc: Exception) -> None:
+        logger.warning("Socket error: %s", exc)
+
+    def connection_lost(self, exc: Exception | None) -> None:
+        self._fh.flush()
+        self._fh.close()
+
+
+async def run(port: int, output_path: Path) -> None:
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+
+    loop = asyncio.get_running_loop()
+    transport, protocol = await loop.create_datagram_endpoint(
+        lambda: SyslogReceiverProtocol(output_path),
+        local_addr=("0.0.0.0", port),
+    )
+
+    logger.info("Listening on UDP :%d → %s", port, output_path)
+
+    stop = loop.create_future()
+    for sig in (signal.SIGINT, signal.SIGTERM):
+        loop.add_signal_handler(sig, stop.set_result, None)
+
+    await stop
+    transport.close()
+    logger.info("Syslog receiver stopped.")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="UDP syslog receiver for Turnstone")
+    parser.add_argument("--port", type=int, default=DEFAULT_PORT)
+    parser.add_argument("--output", default=DEFAULT_OUTPUT)
+    args = parser.parse_args()
+
+    logging.basicConfig(
+        level=logging.INFO,
+        format="%(asctime)s %(levelname)s %(message)s",
+        stream=sys.stdout,
+    )
+
+    asyncio.run(run(args.port, Path(args.output)))
+
+
+if __name__ == "__main__":
+    main()

scripts/turnstone-syslog-receiver.service

@@ -0,0 +1,19 @@
+[Unit]
+Description=Turnstone — UDP syslog receiver (network devices → network-syslog.txt)
+Documentation=https://git.opensourcesolarpunk.com/Circuit-Forge/turnstone
+After=network.target
+
+[Service]
+Type=simple
+ExecStart=/devl/miniconda3/envs/cf/bin/python \
+    /Library/Development/CircuitForge/turnstone/scripts/syslog_receiver.py \
+    --port 5140 \
+    --output /devl/turnstone-cluster/data/network-syslog.txt
+Restart=on-failure
+RestartSec=5s
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=turnstone-syslog-receiver
+
+[Install]
+WantedBy=multi-user.target