feat: setup cache middlewares

internal/middleware/cache.go

@@ -0,0 +1,28 @@
+package middleware
+
+import "net/http"
+
+// CacheStatic wraps a handler to set long-lived cache headers for static assets.
+// Assets use query-string cache busting (?v=<timestamp>), so it's safe to cache
+// them indefinitely — the URL changes when the content changes.
+func CacheStatic(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
+		h.ServeHTTP(w, r)
+	})
+}
+
+// NoCacheDynamic sets Cache-Control: no-cache on responses so browsers always
+// revalidate with the server. This prevents stale HTML from being shown after
+// navigation (e.g. back button) while still allowing conditional requests.
+func NoCacheDynamic(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Skip static assets — they're handled by CacheStatic.
+		if len(r.URL.Path) >= 8 && r.URL.Path[:8] == "/assets/" {
+			next.ServeHTTP(w, r)
+			return
+		}
+		w.Header().Set("Cache-Control", "no-cache")
+		next.ServeHTTP(w, r)
+	})
+}