v2.0.0: Fix compatibility, simplify code, eliminate vulnerabilities

[Copilot]

Full review pass: fix bugs that break on modern Node, replace fragile dependencies, resolve all npm audit vulnerabilities, add tests and CI.

Bug fixes

• new Buffer() → Buffer.from() (removed since Node 10)
• .mv().then(err => ...) — .then() receives resolved value, not error; split into .then()/.catch()
• Undeclared usageMessage variable (implicit global)
• SSL cert/key paths resolved relative to __dirname instead of process.cwd()
• Upload destination resolved relative to __dirname instead of user-specified path
• File path extraction via string slicing → path.dirname() / path.basename()
• Malformed <a/> close tag in receive form HTML

Compatibility

• require('node:os') → require('os') (prefix requires Node 14.18+)
• clipboardy@3 (ESM-only) → clipboardy@2 (CommonJS)
• GitHub fork serve-handler → official serve-handler@6.1.6 with inline prefix strip
• Added engines: { node: ">=14.0.0" }
• Removed deprecated preferGlobal
• Added missing -q/--receive-port CLI option (was in README but not in code)
• Added type annotations to all yargs options

Security

• Express 4.18.1 → 4.21.2 — 12 → 0 npm audit vulnerabilities
• Escaped upload path in post-upload alert to prevent XSS

Tests

• 11 tests (unit + integration) using only built-in assert — no framework dependency
• Covers: utils, config defaults, directory serving, file download, receive form, upload rejection, CLI --help/--version

CI/CD

• Updated publish workflow to run tests across Node 14/16/18/20/22 as a required test job before the publish job (needs: test)
• Added new ci.yml workflow that runs the same test matrix on every push and PR to master/main
• Updated actions/checkout and actions/setup-node from v2 to v4

[parvardegr]

@copilot add a step in ci/cd to run the tests also before publishing, maybe as the first step

[Copilot]

@copilot add a step in ci/cd to run the tests also before publishing, maybe as the first step

Done. Updated the publish workflow to run tests across Node 14/16/18/20/22 as a test job that must pass before the publish job runs (needs: test). Also added a separate ci.yml workflow that runs the same test matrix on every push and PR to master/main. See commit ci: add test step before publish, add CI workflow for PRs.