feat(snmp): add configurable SNMP runtime units with v4.3 migration support

ts/snmp/types.ts

@@ -58,6 +58,11 @@ export interface IOidSet {
  */
 export type TUpsModel = 'cyberpower' | 'apc' | 'eaton' | 'tripplite' | 'liebert' | 'custom';
 
+/**
+ * Runtime unit for battery runtime SNMP values
+ */
+export type TRuntimeUnit = 'minutes' | 'seconds' | 'ticks';
+
 /**
  * SNMP Configuration interface
  */
@@ -96,6 +101,8 @@ export interface ISnmpConfig {
   upsModel?: TUpsModel;
   /** Custom OIDs when using custom UPS model */
   customOIDs?: IOidSet;
+  /** Unit of the battery runtime SNMP value. Overrides model-based auto-detection when set. */
+  runtimeUnit?: TRuntimeUnit;
 }
 
 /**