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/cache/model/entry.rs

@@ -333,8 +333,7 @@ impl Settings {
             if transformed {
                 value.push_str("; transformed");
             }
-            headers.append(
-                "cache-status",
+            headers.append(::http::header::CACHE_STATUS,
                 HeaderValue::from_str(&value).expect("generated Cache-Status member"),
             );
         }