feat: corporate ATS scrapers (Ashby, Greenhouse), O&G, government boards, posted_date fixes

add WorkingNomads + SkipTheDrive scrapers (social media, CS, entry-level focus)

fix: _exec returns conn for SQLite instead of cursor + add 6 new job boards (Bruntwork, ScaleArmy, crypto/web3)

feat: add Neon PostgreSQL support via DATABASE_URL + Fly.io deployment config

fix: scrapers, cron, design, filters, categories, graduate detection

Initial commit: Joblin platform