feat(agent): add durable existing-agent credential transitions

backend/app/agent_zones/repository.py

@@ -250,6 +250,50 @@ class AgentZoneRepository:
         finally:
             connection.close()
 
+    def get_agent_configuration(self, agent_id: str) -> dict | None:
+        connection = self._connection_factory()
+        try:
+            with connection.cursor(row_factory=dict_row) as cur:
+                cur.execute(
+                    """
+                    SELECT
+                        agent.agent_id,
+                        agent.site_id,
+                        agent.agent_zone_id,
+                        coalesce(site.name, agent.site_name) AS site_name,
+                        zone.name AS agent_zone_name,
+                        zone.is_enabled AS agent_zone_enabled,
+                        coalesce(
+                            array_agg(
+                                network.network::text
+                                ORDER BY network.network::text, network.id
+                            ) FILTER (WHERE network.id IS NOT NULL),
+                            ARRAY[]::text[]
+                        ) AS networks
+                    FROM minerops_site_agents AS agent
+                    LEFT JOIN sites AS site
+                      ON site.id = agent.site_id
+                    LEFT JOIN agent_zones AS zone
+                      ON zone.id = agent.agent_zone_id
+                    LEFT JOIN agent_zone_network_ranges AS network
+                      ON network.agent_zone_id = zone.id
+                    WHERE agent.agent_id = %s
+                    GROUP BY
+                        agent.agent_id,
+                        agent.site_id,
+                        agent.agent_zone_id,
+                        site.name,
+                        agent.site_name,
+                        zone.name,
+                        zone.is_enabled
+                    """,
+                    (agent_id,),
+                )
+                row = cur.fetchone()
+                return dict(row) if row else None
+        finally:
+            connection.close()
+
     def assign_miners_to_zone(
         self, miner_ids: Iterable[UUID], agent_zone_id: UUID
     ) -> dict[UUID, str]: