fix(packaging): move templates/ into decnet/ package so they ship with pip install

The docker build contexts and syslog_bridge.py lived at repo root, which
meant setuptools (include = ["decnet*"]) never shipped them. Agents
installed via `pip install $RELEASE_DIR` got site-packages/decnet/** but no
templates/, so every deploy blew up in deployer._sync_logging_helper with
FileNotFoundError on templates/syslog_bridge.py.

Move templates/ -> decnet/templates/ and declare it as setuptools
package-data. Path resolutions in services/*.py and engine/deployer.py drop
one .parent since templates now lives beside the code. Test fixtures,
bandit exclude path, and coverage omit glob updated to match.

decnet/templates/mongodb/server.py

@@ -0,0 +1,127 @@
+#!/usr/bin/env python3
+"""
+MongoDBserver.
+Implements the MongoDB wire protocol OP_MSG/OP_QUERY handshake. Responds
+to isMaster/hello, listDatabases, and authenticate commands. Logs all
+received messages as JSON.
+"""
+
+import asyncio
+import os
+import struct
+from syslog_bridge import syslog_line, write_syslog_file, forward_syslog
+
+NODE_NAME = os.environ.get("NODE_NAME", "mongodb")
+SERVICE_NAME   = "mongodb"
+LOG_TARGET = os.environ.get("LOG_TARGET", "")
+PORT = int(os.environ.get("PORT", "27017"))
+
+# Minimal BSON helpers
+def _bson_str(key: str, val: str) -> bytes:
+    k = key.encode() + b"\x00"
+    v = val.encode() + b"\x00"
+    return b"\x02" + k + struct.pack("<I", len(v)) + v
+
+def _bson_int32(key: str, val: int) -> bytes:
+    return b"\x10" + key.encode() + b"\x00" + struct.pack("<i", val)
+
+def _bson_bool(key: str, val: bool) -> bytes:
+    return b"\x08" + key.encode() + b"\x00" + (b"\x01" if val else b"\x00")
+
+def _bson_doc(*fields: bytes) -> bytes:
+    body = b"".join(fields) + b"\x00"
+    return struct.pack("<I", len(body) + 4) + body
+
+def _op_reply(request_id: int, doc: bytes) -> bytes:
+    # OP_REPLY header: total_len(4), req_id(4), response_to(4), opcode(4)=1,
+    #                  flags(4), cursor_id(8), starting_from(4), number_returned(4), docs
+    header = struct.pack(
+        "<iiiiiqii",
+        16 + 20 + len(doc),  # total length
+        0,                    # request id
+        request_id,           # response to
+        1,                    # OP_REPLY
+        0,                    # flags
+        0,                    # cursor id (int64)
+        0,                    # starting from
+        1,                    # number returned
+    )
+    return header + doc
+
+def _op_msg(request_id: int, doc: bytes) -> bytes:
+    payload = b"\x00" + doc
+    flag_bits = struct.pack("<I", 0)
+    msg_body = flag_bits + payload
+    header = struct.pack("<iiii",
+        16 + len(msg_body),
+        1,
+        request_id,
+        2013,
+    )
+    return header + msg_body
+
+def _log(event_type: str, severity: int = 6, **kwargs) -> None:
+    line = syslog_line(SERVICE_NAME, NODE_NAME, event_type, severity, **kwargs)
+    write_syslog_file(line)
+    forward_syslog(line, LOG_TARGET)
+
+
+class MongoDBProtocol(asyncio.Protocol):
+    def __init__(self):
+        self._transport = None
+        self._peer = None
+        self._buf = b""
+
+    def connection_made(self, transport):
+        self._transport = transport
+        self._peer = transport.get_extra_info("peername", ("?", 0))
+        _log("connect", src=self._peer[0], src_port=self._peer[1])
+
+    def data_received(self, data):
+        self._buf += data
+        while len(self._buf) >= 16:
+            msg_len = struct.unpack("<I", self._buf[:4])[0]
+            if msg_len < 16 or msg_len > 48 * 1024 * 1024:
+                self._transport.close()
+                self._buf = b""
+                return
+            if len(self._buf) < msg_len:
+                break
+            msg = self._buf[:msg_len]
+            self._buf = self._buf[msg_len:]
+            self._handle_message(msg)
+
+    def _handle_message(self, msg: bytes):
+        if len(msg) < 16:
+            return
+        request_id = struct.unpack("<I", msg[4:8])[0]
+        opcode = struct.unpack("<I", msg[12:16])[0]
+        _log("message", src=self._peer[0], opcode=opcode, length=len(msg))
+
+        # Build a generic isMaster-style OK response
+        reply_doc = _bson_doc(
+            _bson_bool("ismaster", True),
+            _bson_int32("maxWireVersion", 17),
+            _bson_int32("minWireVersion", 0),
+            _bson_str("version", "6.0.5"),
+            _bson_int32("ok", 1),
+        )
+        if opcode == 2013:  # OP_MSG
+            self._transport.write(_op_msg(request_id, reply_doc))
+        else:
+            self._transport.write(_op_reply(request_id, reply_doc))
+
+    def connection_lost(self, exc):
+        _log("disconnect", src=self._peer[0] if self._peer else "?")
+
+
+async def main():
+    _log("startup", msg=f"MongoDB server starting as {NODE_NAME}")
+    loop = asyncio.get_running_loop()
+    server = await loop.create_server(MongoDBProtocol, "0.0.0.0", PORT)  # nosec B104
+    async with server:
+        await server.serve_forever()
+
+
+if __name__ == "__main__":
+    asyncio.run(main())