perf: Switch Whisper to tiny.en (10x faster), increase proxy+uvicorn timeouts to 120s for CPU inference

feat: Auto-seed demo account on Docker startup — login with demo@innervoice.app / password

fix: Wait for backend health check before starting frontend — prevents race condition during model loading

fix: Complete Dockerfile rewrite — multi-stage build with Node 20 base, Python3 via apt, CPU-only PyTorch, and .dockerignore

chore: Add Dockerfile, start.sh, and Next.js rewrites to support unified single-port deployment on Hugging Face Spaces