refactor(debt): resolve all 10 technical debt items from audit

chore: finalize Sprint P2 & P3 optimizations, baseline prisma migrations, and update technical audit docs

fix: correct pino transport syntax and cleanup logging types

feat: implement Phase 4 (Quota management, centralized logging, and env sync)

feat: Premium Onboarding with Meta SDK and Technical Debt resolution

Fix: Add Garbage Collector (GC) for media and temp files