feat: zero-touch Agent — central scheduler, central pause, delta sync, discovery-driven installer

Hub: installations.processing_enabled / sync_interval_seconds / last_sync_* (migration 0026).
The first heartbeat of an installation without coverage queues exactly one INITIAL_SYNC;
afterwards one SYNC_INCREMENTAL per interval (idempotent, backs off on failure). One fiscal
job at a time per Agent (FIFO, stale RUNNING recovery). Job completion now updates the
coverage snapshot, blockers and JOB_STARTED/COMPLETED/FAILED events. Panel: Sincronizar
agora / Reprocessar tudo / Pausar / Retomar + status; pause is enforced Hub-side.
Agent: local AGENT_JOBS_ENABLED is ignored (central control); SYNC_INCREMENTAL re-classifies
only new/changed products via a per-product fingerprint+decision cache and rebuilds coverage
from it; results carry operational summary and blockers; Firebird credentials come from a
DPAPI firebird.bin. Setup: read-only SGV Firebird discovery (auto-select only when
unambiguous, wizard chooser otherwise), starts the service, waits for the first heartbeat,
upgrade-in-place mode. All jobs stay read-only (FIREBIRD_WRITES=0). Version 1.1.3.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

central/alembic/versions/0026_central_processing_control.py

@@ -0,0 +1,24 @@
+"""Central processing control + sync bookkeeping per installation.
+
+Revision ID: 0026_central_processing_control
+Revises: 0025_tenant_external_cnpj
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = "0026_central_processing_control"
+down_revision = "0025_tenant_external_cnpj"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column("installations", sa.Column("processing_enabled", sa.Boolean(), nullable=False, server_default="true"))
+    op.add_column("installations", sa.Column("sync_interval_seconds", sa.Integer(), nullable=False, server_default="1800"))
+    op.add_column("installations", sa.Column("last_sync_at", sa.DateTime(timezone=True), nullable=True))
+    op.add_column("installations", sa.Column("last_sync_changed", sa.Integer(), nullable=True))
+
+
+def downgrade():
+    for column in ("last_sync_changed", "last_sync_at", "sync_interval_seconds", "processing_enabled"):
+        op.drop_column("installations", column)