Add NoCache middleware for authenticated pages (closes #61)

internal/middleware/middleware.go

@@ -265,6 +265,26 @@ func (s *Middleware) SecurityHeaders() func(http.Handler) http.Handler {
 	}
 }
 
+// NoCache returns middleware that instructs browsers and
+// intermediary proxies not to cache the response. It sets
+// Cache-Control: no-store and Pragma: no-cache (the latter for
+// older HTTP/1.0 intermediaries). Apply it to authenticated pages
+// so webhook configuration and captured event data are not stored
+// by caches.
+func (s *Middleware) NoCache() func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(
+			w http.ResponseWriter,
+			r *http.Request,
+		) {
+			w.Header().Set("Cache-Control", "no-store")
+			w.Header().Set("Pragma", "no-cache")
+
+			next.ServeHTTP(w, r)
+		})
+	}
+}
+
 // MaxBodySize returns middleware that limits the request body size
 // for POST requests. If the body exceeds the given limit in
 // bytes, the server returns 413 Request Entity Too Large. This

internal/middleware/middleware_test.go

@@ -387,6 +387,45 @@ func TestRequireAuth_UnauthenticatedSession_RedirectsToLogin(
 	assert.Equal(t, "/pages/login", w.Header().Get("Location"))
 }
 
+// --- NoCache Middleware Tests ---
+
+func TestNoCache_SetsHeaders(t *testing.T) {
+	t.Parallel()
+
+	m, _ := testMiddleware(t, config.EnvironmentDev)
+
+	var called bool
+
+	handler := m.NoCache()(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			called = true
+
+			w.WriteHeader(http.StatusOK)
+		},
+	))
+
+	req := httptest.NewRequestWithContext(
+		context.Background(),
+		http.MethodGet, "/sources", nil,
+	)
+	w := httptest.NewRecorder()
+
+	handler.ServeHTTP(w, req)
+
+	assert.True(
+		t, called,
+		"NoCache middleware should call the next handler",
+	)
+	assert.Equal(
+		t, "no-store",
+		w.Header().Get("Cache-Control"),
+	)
+	assert.Equal(
+		t, "no-cache",
+		w.Header().Get("Pragma"),
+	)
+}
+
 // --- Helper Tests ---
 
 func TestIpFromHostPort(t *testing.T) {