refactor: simplify mqtt pipeline state and remove event table

backend/app/mqtt/parser_worker.py

@@ -2,45 +2,33 @@ from __future__ import annotations
 
 import logging
 import time
-from datetime import timedelta
 
 from sqlmodel import Session
 
 from app.core.config import settings
 from app.core.db import engine
-from app.models import TerminalMessageRaw, get_datetime_utc
+from app.models import TerminalMessageRaw
 from app.mqtt.parsers.mixed import parse_mixed_payload
 from app.mqtt.repository import (
     fetch_pending_rows_for_update,
     mark_failed,
-    mark_processing,
     mark_succeeded,
-    write_events_and_update_state,
+    update_device_state_from_events,
 )
 
 logger = logging.getLogger(__name__)
 
 
-def _next_retry_delay_seconds(attempts: int) -> int:
-    # Bounded exponential backoff: 30s, 60s, 120s, ... capped to 15m.
-    return int(min(30 * (2 ** max(attempts - 1, 0)), 900))
-
-
 def _process_one_row(*, session: Session, row: TerminalMessageRaw) -> None:
-    mark_processing(session=session, row=row)
-    session.commit()
-
     try:
         events = parse_mixed_payload(row.payload_bytes)
-        write_events_and_update_state(session=session, row=row, events=events)
+        update_device_state_from_events(session=session, row=row, events=events)
         mark_succeeded(session=session, row=row)
     except Exception as exc:  # pragma: no cover - safety net path
-        delay = _next_retry_delay_seconds(row.parse_attempts)
         mark_failed(
             session=session,
             row=row,
             parse_error=str(exc),
-            next_retry_at=get_datetime_utc() + timedelta(seconds=delay),
         )
 
     session.commit()