implement securityheadersfilter to harden http responses (#91)

* Add SecurityHeadersFilter for hardened HTTP responses

* Add SecurityHeadersFilter for hardened HTTP responses

* Changed X-XSS-Protection value to recommended 0,

* address code review feedback from CodeRabbit

* Add @global annotation to SecurityHeadersFilter for automatic registration

* Removed line of code in App.java

Author: johanbriger

src/main/java/org/juv25d/App.java

@@ -1,16 +1,13 @@
 package org.juv25d;
 
-import org.juv25d.filter.IpFilter;
-import org.juv25d.filter.LoggingFilter;
-import org.juv25d.filter.RateLimitingFilter;
+import org.juv25d.filter.*;
 import org.juv25d.logging.ServerLogging;
 import org.juv25d.http.HttpParser;
 import org.juv25d.plugin.NotFoundPlugin; // New import
 import org.juv25d.plugin.StaticFilesPlugin;
 import org.juv25d.router.SimpleRouter; // New import
 import org.juv25d.util.ConfigLoader;
-import org.juv25d.filter.RedirectFilter;
-import org.juv25d.filter.RedirectRule;
+
 import java.util.List;
 
 import java.util.Set;
@@ -23,6 +20,9 @@ public static void main(String[] args) {
         HttpParser httpParser = new HttpParser();
 
         Pipeline pipeline = new Pipeline();
+
+        pipeline.addGlobalFilter(new SecurityHeadersFilter(), 0);
+
         // Configure redirect rules
         List<RedirectRule> redirectRules = List.of(
             new RedirectRule("/old-page", "/new-page", 301),
@@ -31,7 +31,6 @@ public static void main(String[] args) {
         );
         pipeline.addGlobalFilter(new RedirectFilter(redirectRules), 0);
 
-
         // IP filter is enabled but configured with open access during development
         // White/blacklist can be tightened when specific IP restrictions are decided
         pipeline.addGlobalFilter(new IpFilter(

src/main/java/org/juv25d/filter/SecurityHeadersFilter.java

@@ -0,0 +1,31 @@
+
+package org.juv25d.filter;
+
+import org.juv25d.filter.annotation.Global;
+import org.juv25d.http.HttpRequest;
+import org.juv25d.http.HttpResponse;
+import java.io.IOException;
+
+/**
+ * Filter that adds security headers to every HTTP response.
+ * This helps protect against attacks such as Clickjacking and MIME sniffing.
+ */
+@Global(order = 0)
+public class SecurityHeadersFilter implements Filter {
+
+    @Override
+    public void doFilter(HttpRequest req, HttpResponse res, FilterChain chain) throws IOException {
+        try {
+            chain.doFilter(req, res);
+        } finally {
+
+                res.setHeader("X-Content-Type-Options", "nosniff");
+                res.setHeader("X-Frame-Options", "DENY");
+                res.setHeader("X-XSS-Protection", "0");
+                res.setHeader("Referrer-Policy", "no-referrer");
+
+            }
+        }
+    }
+
+