feat: comprehensive production hardening of interview state machine and frontend-backend synchronization

fix: resolve Firebase popup blocks and interview flow failures

fix: resolve white screen and finalize system integration

fix: deep cleanup and auth update

fix: final popup revert

fix: revert to redirect auth

root-fix: first-party auth and sessions

fix: session caching for adblocker bypass

fix: zero-latency auth with fallback

perf: optimize popup trigger speed

fix: switch to popup and add domain logs

fix: add missing loading state

fix: deep logs and persistence

fix: switch to redirect auth

fix: safer firebase init

Phase 2 Complete: Auth, Dashboard, Analytics