Phase 1-2: Migrate to Deno with npm: and node: specifiers

- Created deno.json configuration
- Updated all imports to use npm:net-snmp@3.20.0
- Changed all Node.js built-in imports to node: specifiers
- Updated all .js extensions to .ts in imports
- Created mod.ts as Deno entry point
- Ready for Phase 3: CLI simplification

ts/snmp/index.ts

@@ -4,7 +4,7 @@
  */
 
 // Re-export all public types
-export type { IUpsStatus, IOidSet, TUpsModel, ISnmpConfig } from './types.js';
+export type { IUpsStatus, IOidSet, TUpsModel, ISnmpConfig } from './types.ts';
 
 // Re-export the SNMP manager class
-export { NupstSnmp } from './manager.js';
+export { NupstSnmp } from './manager.ts';