feat: add optional web UI with live scan progress

[lbrezende]

Summary

Adds an optional Flask web UI that surfaces Sherlock's scan progress visually, so users see continuous feedback during a run instead of waiting in silence for the full scan to finish.

Why

A default Sherlock scan checks ~400 sites and takes 1–2 minutes. First-time users often can't tell whether the tool is working, stuck, or done — especially when --print-found stays silent until a match lands. This adds a lightweight, opt-in view to close that feedback gap without touching the CLI.

What's in it

A single-file module (sherlock_project/web.py) wrapping the CLI, with three display modes:

• Found — clean list of matched profiles only
• Live (default) — streaming view: matches appear inline as clickable links, misses stack as red dashes so progress is always visible
• Full log — complete raw output

Plus:

• EN / PT-BR localization with browser auto-detection and persistence
• Live counter of hits and misses
• Line-by-line streaming (no buffering)
• Completely opt-in; the core CLI is untouched

How to run

```bash
pip install flask
python -m sherlock_project.web

http://127.0.0.1:5000

```

Host and port can be overridden with `SHERLOCK_WEB_HOST` and `SHERLOCK_WEB_PORT`.

Notes

• Flask is loaded lazily with a friendly install hint — it is not added as a core dependency
• Username input is validated server-side against `^[A-Za-z0-9_.-]{1,64}$` before being passed to the subprocess
• `ruff check` passes

Happy to adjust scope, placement, or styling based on maintainer preferences.