feat(cli): support home credentials resolution

[kvz]

Summary

• add ~/.transloadit/credentials support to the Node CLI with explicit precedence
• support token or key/secret auth for normal CLI commands while keeping signing/token minting on key/secret
• improve docs, tests, and missing-auth messaging with concrete lookup paths

Validation

• yarn workspace @transloadit/node check
• yarn check

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Restore injected .env vars when file disappears

If loadProjectDotenvIntoProcessEnv() is called again in the same working directory after .env has been removed, this branch clears the bookkeeping state but never restores previously injected keys, so stale values remain in process.env. In a long-lived process that invokes main()/runSig() multiple times, deleted credentials or endpoints can still be used on later invocations, which breaks the documented resolution behavior and can apply outdated auth unexpectedly.

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