refactor: replace 'any' types with proper TypeScript interfaces

Major type safety improvements throughout the codebase:

- Updated DEFAULT_CONFIG version to 4.2
- Replaced 'any' with proper types in systemd.ts:
  * displaySingleUpsStatus now uses IUpsConfig and NupstSnmp types
  * Fixed legacy config handling to use proper IUpsConfig format
  * Removed inline 'any' type annotations

- Replaced 'any' with proper types in daemon.ts:
  * emergencyUps now properly typed as { ups: IUpsConfig, status: ISnmpUpsStatus }
  * Exported IUpsStatus interface for reuse
  * Added ISnmpUpsStatus import to disambiguate from daemon's IUpsStatus

- Replaced 'any' with Record<string, unknown> in migration system:
  * Updated BaseMigration abstract class signatures
  * Updated MigrationRunner.run() signature
  * Updated migration-v4.0-to-v4.1.ts to use proper types
  * Migrations use Record<string, unknown> because they deal with
    unknown config schemas that are being upgraded

Benefits:
- TypeScript now catches type errors at compile time
- Would have caught the ups.thresholds bug earlier
- Better IDE autocomplete and type checking
- More maintainable and self-documenting code

ts/daemon.ts

@@ -4,7 +4,7 @@ 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 type { ISnmpConfig, IUpsStatus as ISnmpUpsStatus } from './snmp/types.ts';
 import { logger, type ITableColumn } from './logger.ts';
 import { MigrationRunner } from './migrations/index.ts';
 import { theme, symbols, getBatteryColor, getRuntimeColor, formatPowerStatus } from './colors.ts';
@@ -76,7 +76,7 @@ export interface INupstConfig {
 /**
  * UPS status tracking interface
  */
-interface IUpsStatus {
+export interface IUpsStatus {
   id: string;
   name: string;
   powerStatus: 'online' | 'onBattery' | 'unknown';
@@ -96,7 +96,7 @@ export class NupstDaemon {
 
   /** Default configuration */
   private readonly DEFAULT_CONFIG: INupstConfig = {
-    version: '4.1',
+    version: '4.2',
     upsDevices: [
       {
         id: 'default',
@@ -171,11 +171,13 @@ export class NupstDaemon {
       const { config: migratedConfig, migrated } = await migrationRunner.run(parsedConfig);
 
       // Save migrated config back to disk if any migrations ran
+      // Cast to INupstConfig since migrations ensure the output is valid
+      const validConfig = migratedConfig as unknown as INupstConfig;
       if (migrated) {
-        this.config = migratedConfig;
+        this.config = validConfig;
         await this.saveConfig(this.config);
       } else {
-        this.config = migratedConfig;
+        this.config = validConfig;
       }
 
       return this.config;
@@ -760,7 +762,7 @@ export class NupstDaemon {
 
         const rows: Array<Record<string, string>> = [];
         let emergencyDetected = false;
-        let emergencyUps: any = null;
+        let emergencyUps: { ups: IUpsConfig; status: ISnmpUpsStatus } | null = null;
 
         // Check all UPS devices
         for (const ups of this.config.upsDevices) {