[gustavofreze]

Please follow the contributing guidelines.

Summary

• Adds the ApplicationEnvironment backed enum with the LOCAL, TEST, DEVELOPMENT, STAGING, and PRODUCTION cases, so a consumer asks isLocal() instead of comparing APP_ENV to a raw string.
• Adds ApplicationEnvironment::current(), which reads APP_ENV through EnvironmentVariable::from, so the same resolution order and the HTTP_ guard apply and a missing variable still raises EnvironmentVariableMissing.
• Adds ApplicationEnvironment::fromAlias(), matching aliases regardless of casing and of surrounding whitespace: local and localhost, test and testing, development, dev, and develop, staging, stage, homolog, and homologation, production and prod.
• Adds ApplicationEnvironmentUnrecognized, raised for a value no environment recognizes, with the accepted aliases in its message.
• Adds the isLocal(), isTest(), isDevelopment(), isStaging(), and isProduction() predicates, plus aliases().
• Documents the new section, the exception, and the no-fallback decision in the README.

The existing API is unchanged.

Related issue

None.

Checklist

• Tests added or updated.
• Documentation updated when applicable.
• make review passes.
• make tests passes.