feat: add MQTT topic parsing and pipeline config

backend/app/mqtt/__init__.py

@@ -0,0 +1 @@
+"""MQTT ingestion pipeline package."""

backend/app/mqtt/topic.py

@@ -0,0 +1,10 @@
+import re
+
+TOPIC_PATTERN = re.compile(r"^terminal/(?P<device_id>[^/]+)/raw$")
+
+
+def extract_device_id(topic: str) -> str:
+    match = TOPIC_PATTERN.match(topic)
+    if match is None:
+        raise ValueError("topic must match terminal/{device_id}/raw")
+    return match.group("device_id")