Enhance grid UI and refactor boot overlay logic

- Updated `MappingProfile.cs` to add detailed mapping for `Envelope` to `EnvelopeDto`, including `EnvelopeTypeTitle`.
- Added a grid persistence hint banner in `EnvelopeSenderPage.razor` with an SVG icon and German message.
- Introduced three new columns (`EnvelopeTypeTitle`, `AddedWhen`, `ChangedWhen`) to the grid in `EnvelopeSenderPage.razor`.
- Refactored boot overlay removal logic in `App.razor` into a reusable function `sfRemoveBootOverlay`.
- Simplified event handling for overlay removal and fallback logic in `App.razor`.
- Adjusted `.sender-grid-wrapper` padding in `sender-page.css` and added styles for the new grid persistence hint banner.

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/App.razor

@@ -44,23 +44,16 @@
     <script src="js/signflow-theme.js"></script>
     <script src="_framework/blazor.web.js"></script>
     <script>
-        // Remove the boot overlay once Blazor has started and enhanced navigation is active.
-        Blazor.addEventListener('enhancedload', function onFirstLoad() {
-            var overlay = document.getElementById('sf-boot-overlay');
-            if (overlay) overlay.style.opacity = '0';
-            setTimeout(function () { if (overlay) overlay.remove(); }, 250);
-            Blazor.removeEventListener('enhancedload', onFirstLoad);
-        });
-        // Also remove when WASM circuit is ready (for non-enhanced pages like /sender)
-        document.addEventListener('blazor-circuit-connected', function () {
+        function sfRemoveBootOverlay() {
             var overlay = document.getElementById('sf-boot-overlay');
             if (overlay) { overlay.style.opacity = '0'; setTimeout(function () { if (overlay) overlay.remove(); }, 250); }
-        }, { once: true });
+        }
+        // Remove on every enhanced navigation (covers both WASM and Server render modes).
+        Blazor.addEventListener('enhancedload', sfRemoveBootOverlay);
+        // Also remove when WASM circuit is ready (for non-enhanced pages like /sender)
+        document.addEventListener('blazor-circuit-connected', sfRemoveBootOverlay, { once: true });
         // Fallback: remove after 4s regardless
-        setTimeout(function () {
-            var overlay = document.getElementById('sf-boot-overlay');
-            if (overlay) overlay.remove();
-        }, 4000);
+        setTimeout(sfRemoveBootOverlay, 4000);
     </script>
 </body>
 

EnvelopeGenerator.Server/EnvelopeGenerator.Server/wwwroot/css/sender-page.css

@@ -199,7 +199,20 @@
 }
 
 .sender-grid-wrapper {
-    padding: 1.5rem 2rem 2rem;
+    padding: 0 2rem 2rem;       /* top padding removed — hint banner provides top spacing */
+}
+
+/* ── Grid persistence hint banner ─────────────────────────────────────────── */
+.sf-grid-persistence-hint {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    padding: 6px 2rem;
+    font-size: 0.72rem;
+    color: rgba(126, 34, 206, 0.65);
+    background: rgba(126, 34, 206, 0.04);
+    border-bottom: 1px solid rgba(126, 34, 206, 0.08);
+    user-select: none;
 }
 
 /* Hide DevExpress empty cells */