Move Upload CSV from navigation menu to Transactions page

Removed "Upload CSV" from the main navigation menu and added an "Upload CSV" button to the Transactions page header. This makes CSV upload more contextual since it's primarily used when viewing/managing transactions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

MoneyMap/Pages/Shared/_Layout.cshtml

@@ -31,9 +31,6 @@
                         <li class="nav-item">
                             <a class="nav-link text-dark" asp-page="/Accounts">Accounts</a>
                         </li>
-                        <li class="nav-item">
-                            <a class="nav-link text-dark" asp-page="/Upload">Upload CSV</a>
-                        </li>
                         <li class="nav-item">
                             <a class="nav-link text-dark" asp-page="/CategoryMappings">Categories</a>
                         </li>

MoneyMap/Pages/Transactions.cshtml

@@ -6,7 +6,10 @@
 
 <div class="d-flex justify-content-between align-items-center mb-3">
     <h2>Transactions</h2>
-    <a asp-page="/Index" class="btn btn-outline-secondary">Back to Dashboard</a>
+    <div class="d-flex gap-2">
+        <a asp-page="/Upload" class="btn btn-primary">Upload CSV</a>
+        <a asp-page="/Index" class="btn btn-outline-secondary">Back to Dashboard</a>
+    </div>
 </div>
 
 <!-- Filters -->