feat: implement mqtt ingestion, parsing, and archive pipeline

backend/app/mqtt/parsers/rtcm.py

@@ -0,0 +1,22 @@
+from __future__ import annotations
+
+
+def summarize_rtcm_types(payload: bytes) -> dict[int, int]:
+    counts: dict[int, int] = {}
+    i = 0
+
+    while i + 6 <= len(payload):
+        if payload[i] != 0xD3:
+            i += 1
+            continue
+
+        length = ((payload[i + 1] & 0x03) << 8) | payload[i + 2]
+        frame_end = i + 3 + length + 3
+        if frame_end > len(payload):
+            break
+
+        message_type = ((payload[i + 3] << 4) | (payload[i + 4] >> 4)) & 0x0FFF
+        counts[message_type] = counts.get(message_type, 0) + 1
+        i = frame_end
+
+    return counts