v0.35.1: performance, AGPL licensing and documentation overhaul

- Web Server reads static files inline; proxy middleware chain flattened
- About window with license summary and project links; AGPL-3.0-or-later
- Rewritten documentation: feature list, screenshots, performance guide
- Fix false spikes in per-Vhost request-rate charts

src/settings.rs

@@ -451,11 +451,11 @@ impl ServerHeader {
         match self.mode {
             ServerMode::Preserve => {}
             ServerMode::Hide => {
-                headers.remove("server");
+                headers.remove(::http::header::SERVER);
             }
             ServerMode::Custom => {
                 if let Ok(value) = self.value.parse() {
-                    headers.insert("server", value);
+                    headers.insert(::http::header::SERVER, value);
                 }
             }
         }