v5.0.0: Modernize dependency stack and migrate to ESLint flat config

[Copilot]

PR #105 updates all major dependencies to current versions and migrates the ESLint configuration to the flat config format. This review applies those changes with one correction identified during review.

Dependency updates

• ajv v6 → v8: extendRefs option removed; migrated to { strict: false, allErrors: true }. error.dataPath → error.instancePath in capabilities.js and dependencies.js
• compare-versions v3 → v6: default export replaced with named export

  // before
  const compareVersions = require("compare-versions");
  compareVersions.compare(apiVersion, "3.8.0", ">=")
  
  // after
  const { compare } = require("compare-versions");
  compare(apiVersion, "3.8.0", ">=")

• fs-extra v9 → v11, @babel/* updated to 7.29.x — no API changes required
• Node.js engine: minimum bumped from >=12 to >=18

ESLint migration

• Removes .eslintrc.js (legacy format); adds eslint.config.js (ESLint v9 flat config)
• Switches from deprecated eslint-plugin-node to eslint-plugin-n
• Fix applied: PR Update packages #105 incorrectly set sourceType: "module" for src/**/*.js in an override block; removed that block since all source files use CommonJS — the global sourceType: "script" is correct

Other cleanup

• Removes unused const { file } = require('jszip') from src/utils.js
• Trailing comma and quote consistency fixes throughout (style only)

Breaking changes

Only the Node.js minimum version requirement (>=18) is a breaking change for consumers. All plugin options, defaults, and output artifacts are unchanged.

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