fix: use relative paths for splash screen logos to support custom BasePath (#1840)

* Initial plan

* fix: use relative paths for splash screen logos to support custom BasePath

Co-authored-by: rnwood <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: rnwood <[email protected]>

Author: Copilot

Rnwood.Smtp4dev/ClientApp/index.html

@@ -37,8 +37,8 @@
 
         <div style="font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; height: 100%; width: 100%; display: flex; align-items: center; justify-content: center; flex-direction: column;">
             <div>
-                <img class="splashlogolight" src="logo.png" />
-                <img class="splashlogodark" src="logo-dark.png" />
+                <img class="splashlogolight" src="./logo.png" />
+                <img class="splashlogodark" src="./logo-dark.png" />
             </div>
             <div style="color: #7c7c7c" id="loading">Loading...</div>
             <div id="oldbrowser" style="display: none; width: 100%; text-align: center; margin: 32px;">