ui: glassmorphism redesign with blue-purple gradient theme

perf: comprehensive optimization — connection pooling, streaming upload, typed errors, password hashing

fix: web upload - remove temp file, return actual Telegram errors

fix: upload auth - hash password before cookie comparison

docs: update README with download-first workflow and security info

ci: add GitHub Actions for CI and release builds

fix: welcome password-only + token persistence + UI polish

feat: full security hardening

fix: allow main page after password set + UI polish

feat: one-click install with web-based setup wizard

init: tgstate Rust rewrite from Python (FastAPI -> Axum)