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/daemon.ts

@@ -1,10 +1,10 @@
-import * as fs from 'fs';
-import * as path from 'path';
-import { exec, execFile } from 'child_process';
-import { promisify } from 'util';
-import { NupstSnmp } from './snmp/manager.js';
-import type { ISnmpConfig } from './snmp/types.js';
-import { logger } from './logger.js';
+import * as fs from "node:fs";
+import * as path from "node:path";
+import { exec, execFile } from "node:child_process";
+import { promisify } from "node:util";
+import { NupstSnmp } from './snmp/manager.ts';
+import type { ISnmpConfig } from './snmp/types.ts';
+import { logger } from './logger.ts';
 
 const execAsync = promisify(exec);
 const execFileAsync = promisify(execFile);