fix(snmp): resolve TypeScript type errors for Deno strict mode

- Add Buffer import from node:buffer to manager.ts and types.ts
- Fix error handling type assertions (error/retryError/stdError as unknown)
- Add explicit type annotation to byte parameter in isPrintableAscii check
- All tests now passing (3 SNMP tests + 10 logger tests)

ts/snmp/types.ts

@@ -2,6 +2,8 @@
  * Type definitions for SNMP module
  */
 
+import { Buffer } from "node:buffer";
+
 /**
  * UPS status interface
  */