Refactor texture handling and update route structure

Moved sessionserver routes to correct directory and removed subdirectory logic from texture file lookup. Updated texture URLs to remove leading slashes and fixed endpoint concatenation. Added default textures for Alex and Steve.

services/authService.js

@@ -56,7 +56,7 @@ async function authenticate({ identifier, password, clientToken, requireUser })
 
     delete userResult.user.password
 
-    const $clientToken = uuidRegex.test(clientToken) ? clientToken : crypto.randomUUID()
+    const $clientToken = clientToken || crypto.randomUUID()
     const accessToken = jwt.sign({
         uuid: userResult.user.uuid,
         username: userResult.user.username,
@@ -120,7 +120,7 @@ async function refreshToken({ previousAccessToken, clientToken, requireUser }) {
 
     await authRepository.invalidateClientSession(previousAccessToken, clientToken)
 
-    const $clientToken = uuidRegex.test(clientToken) ? clientToken : crypto.randomUUID()
+    const $clientToken = clientToken || crypto.randomUUID()
     const newAccessToken = jwt.sign({
         uuid: userResult.user.uuid,
         username: userResult.user.username,