fix: use relative WASM bootstrap script path with base href

- Changed /_framework/blazor.webassembly.js to _framework/blazor.webassembly.js
- Relative path combines with base href="/taxbaik/admin/" to resolve correctly
- WASM files located at /admin/_framework/ (from TaxBaik.Web.Client build)
- Browser will now successfully boot WASM and render dashboard.razor

Resolves 404 error: was requesting /_framework/ (doesn't exist)
Now correctly resolves to: /taxbaik/admin/_framework/ (exists)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/TaxBaik.Web.Client/wwwroot/index.html

@@ -47,7 +47,7 @@
     </div>
 
     <script src="js/admin-session.js"></script>
-    <script src="/_framework/blazor.webassembly.js"></script>
+    <script src="_framework/blazor.webassembly.js"></script>
     <script>
         function initSession() {
             if (window.taxbaikAdminSession) {