✨ Add subject name to generations and backfill data

Introduce a new column for subject names in the generations table and implement a service to backfill missing subject metadata based on image analysis results. :sparkles: Introduce job processing and database updates Add job processing through Solid Queue and configure database for development and queue environments. Update Procfile and README for local job execution. :sparkles: Update download options for image generation Revise download section to include preview and 4K options, enhancing user experience and accessibility of image downloads. :recycle: Refactor code structure for better maintainability Organize and streamline code to enhance readability and future updates. :sparkles: Introduce database management script Add a script to manage the development database, including dumping production data, dropping, and recreating the local database, and syncing assets from Hetzner Object Storage. :sparkles: Introduce BYOK Unlimited plan and update credits Add a new BYOK Unlimited purchase option and update related UI texts and logic to reflect changes in credit usage and purchasing options.