feat: Add build date functionality and enhance documentation pages

- Added a script to save the build date during Docker image build.
- Introduced a build_date property in the Settings class to retrieve the build date from the environment or file.
- Enhanced the homepage to display system statistics including processed files and active integrations.
- Updated the about page with a comprehensive list of features.
- Added new privacy, imprint, cookies, and terms pages with relevant content.
- Improved the license page with related information links.
- Refactored the base template for better mobile responsiveness and footer links.

frontend/templates/license.html

@@ -6,7 +6,7 @@
 <div class="container mx-auto px-4 py-8">
     <h1 class="text-2xl font-bold mb-4">License Information</h1>
     
-    <div class="bg-white shadow-md rounded-lg p-6">
+    <div class="bg-white shadow-md rounded-lg p-6 mb-6">
         <h2 class="text-xl font-semibold mb-4">Apache License 2.0</h2>
         
         <div class="prose">
@@ -19,5 +19,19 @@
             contribute to the project.
         </p>
     </div>
+    
+    <div class="bg-white shadow-md rounded-lg p-6">
+        <h2 class="text-xl font-semibold mb-4">Related Information</h2>
+        <p class="mb-3 text-gray-600">
+            While this license governs the use of our software, please also review our 
+            <a href="/terms" class="text-blue-600 hover:underline">Terms of Service</a> and 
+            <a href="/privacy" class="text-blue-600 hover:underline">Privacy Policy</a> for 
+            information about using the DocuElevate service.
+        </p>
+        <p class="text-gray-600">
+            For more information about DocuElevate, please visit the 
+            <a href="/about" class="text-blue-600 hover:underline">About page</a>.
+        </p>
+    </div>
 </div>
 {% endblock %}