Add option to skip recurring jobs via environment variable

[iamradioactive]

Closes #558

Problem
Users need a way to disable recurring jobs in specific environments (staging, review apps, development) without modifying configuration files or CLI commands. This is particularly useful for:

• Staging environments where you don't want production cron jobs running
• Review/preview apps that should focus on testing features, not running scheduled tasks
• Development environments where recurring jobs might interfere with testing

Solution

• Adds support for the SOLID_QUEUE_SKIP_RECURRING environment variable that mirrors the existing --skip-recurring CLI option functionality.

Changes

• Configuration: Modified default_options in Configuration class to read SOLID_QUEUE_SKIP_RECURRING environment variable
• Tests: Added test coverage with new with_env test helper
• Documentation: Updated README with usage examples and use cases

Usage

SOLID_QUEUE_SKIP_RECURRING=true bin/jobs