Update branding to "signFLOW" for consistency

The footer text in `MainLayout.razor` and the header title in `IndexPage.razor` have been updated to change the branding from "SignFlow" to "signFLOW". This change ensures consistent presentation of the brand across the application by adjusting the capitalization.

EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Layout/MainLayout.razor

@@ -22,7 +22,7 @@
     </main>
     <footer class="receiver-footer">
         <div class="receiver-footer__left">
-            <span>&copy; SignFlow 2023-2024 <a href="https://digitaldata.works" target="_blank" rel="noopener">Digital Data GmbH</a></span>
+            <span>&copy; signFLOW 2023-2024 <a href="https://digitaldata.works" target="_blank" rel="noopener">Digital Data GmbH</a></span>
             <span class="receiver-footer__sep">&#124;</span>
             <a href="@GetPrivacyPolicyPath()" target="_blank" rel="noopener">@L("PrivacyPolicy", "Datenschutz")</a>
         </div>

EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Pages/IndexPage.razor

@@ -26,7 +26,7 @@
                 </svg>
             }
             <div>
-                <h1 class="home-hero-header__title">SignFlow</h1>
+                <h1 class="home-hero-header__title">signFLOW</h1>
                 <p class="home-hero-header__subtitle">@L("Index_Subtitle", "Willkommen im eSign-Portal")</p>
             </div>
         </div>