refactor: simplify mqtt pipeline state and remove event table

backend/app/alembic/versions/c6d7e8f90123_drop_terminal_observation_event.py

@@ -0,0 +1,60 @@
+"""drop terminal observation event table
+
+Revision ID: c6d7e8f90123
+Revises: b4c5d6e7f809
+Create Date: 2026-03-19 18:20:00.000000
+
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = "c6d7e8f90123"
+down_revision = "b4c5d6e7f809"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.drop_table("terminal_observation_event")
+
+
+def downgrade() -> None:
+    op.create_table(
+        "terminal_observation_event",
+        sa.Column("id", sa.Uuid(), nullable=False),
+        sa.Column("raw_id", sa.Uuid(), nullable=False),
+        sa.Column("device_id", sa.String(length=255), nullable=False),
+        sa.Column("event_time", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("event_type", sa.String(length=64), nullable=False),
+        sa.Column("payload_json", sa.JSON(), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False),
+        sa.ForeignKeyConstraint(["raw_id"], ["terminal_message_raw.id"]),
+        sa.PrimaryKeyConstraint("id"),
+    )
+    op.create_index(
+        op.f("ix_terminal_observation_event_device_id"),
+        "terminal_observation_event",
+        ["device_id"],
+        unique=False,
+    )
+    op.create_index(
+        op.f("ix_terminal_observation_event_event_time"),
+        "terminal_observation_event",
+        ["event_time"],
+        unique=False,
+    )
+    op.create_index(
+        op.f("ix_terminal_observation_event_event_type"),
+        "terminal_observation_event",
+        ["event_type"],
+        unique=False,
+    )
+    op.create_index(
+        op.f("ix_terminal_observation_event_raw_id"),
+        "terminal_observation_event",
+        ["raw_id"],
+        unique=False,
+    )