feat(migrations): add migration system for v3→v4 config format

- Create abstract BaseMigration class with order, shouldRun(), migrate()
- Add MigrationRunner to execute migrations in order
- Add Migration v1→v2 (snmp → upsDevices)
- Add Migration v3→v4 (upsList → upsDevices)
- Update INupstConfig with version field
- Update loadConfig() to run migrations automatically
- Update saveConfig() to ensure version field and remove legacy fields
- Update Docker test scripts to use real UPS data from .nogit/env.json
- Remove colors.bright (not available in @std/fmt/colors)

Config migrations allow users to jump versions (e.g., v1→v4) with all
intermediate migrations running automatically. Version field tracks
config format for future migrations.

ts/migrations/migration-runner.ts

@@ -0,0 +1,69 @@
+import { BaseMigration } from './base-migration.ts';
+import { MigrationV1ToV2 } from './migration-v1-to-v2.ts';
+import { MigrationV3ToV4 } from './migration-v3-to-v4.ts';
+import { logger } from '../logger.ts';
+
+/**
+ * Migration runner
+ *
+ * Discovers all available migrations, sorts them by order,
+ * and runs applicable migrations in sequence.
+ */
+export class MigrationRunner {
+  private migrations: BaseMigration[];
+
+  constructor() {
+    // Register all migrations here
+    this.migrations = [
+      new MigrationV1ToV2(),
+      new MigrationV3ToV4(),
+      // Add future migrations here (v4→v5, v5→v6, etc.)
+    ];
+
+    // Sort by order to ensure they run in sequence
+    this.migrations.sort((a, b) => a.order - b.order);
+  }
+
+  /**
+   * Run all applicable migrations on the config
+   *
+   * @param config - Raw configuration object to migrate
+   * @returns Migrated configuration and whether migrations ran
+   */
+  async run(config: any): Promise<{ config: any; migrated: boolean }> {
+    let currentConfig = config;
+    let anyMigrationsRan = false;
+
+    logger.dim('Checking for required config migrations...');
+
+    for (const migration of this.migrations) {
+      const shouldRun = await migration.shouldRun(currentConfig);
+
+      if (shouldRun) {
+        logger.info(`Running ${migration.getName()}...`);
+        currentConfig = await migration.migrate(currentConfig);
+        anyMigrationsRan = true;
+      }
+    }
+
+    if (anyMigrationsRan) {
+      logger.success('Configuration migrations complete');
+    } else {
+      logger.dim('No migrations needed');
+    }
+
+    return {
+      config: currentConfig,
+      migrated: anyMigrationsRan,
+    };
+  }
+
+  /**
+   * Get all registered migrations
+   *
+   * @returns Array of all migrations sorted by order
+   */
+  getMigrations(): BaseMigration[] {
+    return [...this.migrations];
+  }
+}