nginx config formatter

Reindents an nginx configuration by block depth. Braces set the level, directives sit inside, and blank lines between blocks are kept to one.

nginx configuration is a tree of blocks, and depth is the only thing indentation communicates — the parser ignores whitespace entirely. What indentation buys you is seeing which `location` a directive belongs to, and that matters because nginx directive inheritance is genuinely surprising: a directive in a `location` block does **not** merge with the same directive in the enclosing `server` block, it replaces it. The classic case is `proxy_set_header`. Setting one header inside a `location` discards every `proxy_set_header` from the enclosing scope, so the `Host` header you set at server level silently disappears. Seeing the nesting clearly is how you notice. One thing this does not do is validate. `nginx -t` is the only authority on whether a config is correct, and it checks things no formatter can — that referenced files exist, that a certificate matches its key, that a directive is legal in the context it appears in.