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/base-migration.ts

@@ -0,0 +1,54 @@
+/**
+ * Abstract base class for configuration migrations
+ *
+ * Each migration represents an upgrade from one config version to another.
+ * Migrations run in order based on the `order` field, allowing users to jump
+ * multiple versions (e.g., v1 → v4 runs migrations 2, 3, and 4).
+ */
+export abstract class BaseMigration {
+  /**
+   * Migration order number
+   * - Order 2: v1 → v2
+   * - Order 3: v2 → v3
+   * - Order 4: v3 → v4
+   * etc.
+   */
+  abstract readonly order: number;
+
+  /**
+   * Source version this migration upgrades from
+   * e.g., "1.x", "3.x"
+   */
+  abstract readonly fromVersion: string;
+
+  /**
+   * Target version this migration upgrades to
+   * e.g., "2.0", "4.0"
+   */
+  abstract readonly toVersion: string;
+
+  /**
+   * Check if this migration should run on the given config
+   *
+   * @param config - Raw configuration object to check
+   * @returns True if migration should run, false otherwise
+   */
+  abstract shouldRun(config: any): Promise<boolean>;
+
+  /**
+   * Perform the migration on the given config
+   *
+   * @param config - Raw configuration object to migrate
+   * @returns Migrated configuration object
+   */
+  abstract migrate(config: any): Promise<any>;
+
+  /**
+   * Get human-readable name for this migration
+   *
+   * @returns Migration name
+   */
+  getName(): string {
+    return `Migration ${this.fromVersion} → ${this.toVersion}`;
+  }
+}