perf(web): add gzip compression + cache-control headers for static assets

- Add CompressionLayer to web router for gzip compression of JS/CSS/JSON/SVG
- Add Cache-Control header (7 days + stale-while-revalidate) via SetResponseHeaderLayer
- Add 'set-header' feature to tower-http dependency
- Result: 67-85% reduction in transfer size for all static assets

src/interfaces/web/mod.rs

@@ -1,7 +1,10 @@
 use crate::common::config::AppConfig;
 use crate::common::di::AppState;
+use axum::http::header::{CACHE_CONTROL, HeaderValue};
 use axum::{Router, response::Html, routing::get};
+use tower_http::compression::CompressionLayer;
 use tower_http::services::ServeDir;
+use tower_http::set_header::SetResponseHeaderLayer;
 
 /// Creates web routes for serving static files
 pub fn create_web_routes() -> Router<AppState> {
@@ -9,14 +12,25 @@ pub fn create_web_routes() -> Router<AppState> {
     let config = AppConfig::from_env();
     let static_path = config.static_path.clone();
 
+    // Static assets (JS, CSS, JSON, SVG, ICO) served via ServeDir
+    // with gzip compression and aggressive caching (7 days).
+    // HTML pages are served via explicit routes (include_str!) and
+    // do NOT pass through these layers.
+    let static_service = ServeDir::new(static_path);
+
     Router::new()
         // Add specific routes for clean URLs (without .html)
         .route("/login", get(serve_login_page))
         .route("/profile", get(serve_profile_page))
         .route("/admin", get(serve_admin_page))
         .route("/shared", get(serve_shared_page))
-        // Serve static files
-        .fallback_service(ServeDir::new(static_path))
+        // Serve static files with compression + cache headers
+        .fallback_service(static_service)
+        .layer(CompressionLayer::new())
+        .layer(SetResponseHeaderLayer::if_not_present(
+            CACHE_CONTROL,
+            HeaderValue::from_static("public, max-age=604800, stale-while-revalidate=86400"),
+        ))
 }
 
 /// Serve the login page