Improve popup layout and scrolling behavior

Updated `CreateEnvelopeWizardPopup.razor` to enforce consistent popup dimensions by setting height properties to `85vh` and disabling scrolling.

Enhanced `sender-page.css` with new classes to manage flexible layouts and scrolling behavior for the wizard's stepper and step content. Removed fixed height and scrolling constraints from `.sender-create-wizard__receiver-existing-list` for better layout flexibility.

These changes improve the user experience by ensuring consistent dimensions, reducing unnecessary scrolling, and maintaining a structured layout.

EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Components/Sender/CreateEnvelopeWizardPopup.razor

@@ -17,6 +17,10 @@
          HeaderText="@L("SenderWizard_Header", "Neuen Umschlag erstellen")"
          Width="90vw"
          MaxWidth="90vw"
+         Height="85vh"
+         MinHeight="85vh"
+         MaxHeight="85vh"
+         Scrollable="false"
          ShowFooter="true"
          CloseOnOutsideClick="false"
          ShowCloseButton="true"

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

@@ -1108,13 +1108,85 @@
     grid-template-columns: minmax(0, 1fr) minmax(240px, 280px);
     gap: 0.85rem;
     align-items: stretch;
-    min-height: min(66vh, 620px);
     transition: grid-template-columns 220ms ease 0.2s, gap 220ms ease 0.2s;
 }
 
+.sender-create-wizard-popup.dxbl-modal-root,
+.sender-create-wizard-popup .dxbl-modal-root,
+.sender-create-wizard-popup .dxbl-modal,
+.sender-create-wizard-popup .dxbl-modal-dialog,
+.sender-create-wizard-popup .dxbl-modal-content,
+.sender-create-wizard-popup .dxbl-popup,
+.sender-create-wizard-popup.dxbl-popup {
+    height: 85vh !important;
+    max-height: 85vh !important;
+    display: flex !important;
+    flex-direction: column !important;
+}
+
+.sender-create-wizard-popup .dxbl-modal-body,
 .sender-create-wizard-popup .dxbl-popup-content {
-    max-height: min(78vh, 760px);
+    flex: 1 1 auto !important;
-    overflow: auto;
+    height: auto !important;
+    min-height: 0 !important;
+    max-height: none !important;
+    overflow: hidden !important;
+    display: flex !important;
+    flex-direction: column !important;
+}
+
+.sender-create-wizard-popup .dxbl-popup-content > .sender-create-wizard,
+.sender-create-wizard-popup .sender-create-wizard,
+.sender-create-wizard-popup .sender-create-wizard__body-layout {
+    flex: 1 1 auto !important;
+    height: auto !important;
+    min-height: 0 !important;
+    overflow: hidden !important;
+}
+
+/* Scroll only inside the stepper content, so the body never resizes. */
+.sender-create-wizard__stepper-shell {
+    min-height: 0 !important;
+    overflow: hidden !important;
+    display: flex !important;
+    flex-direction: column !important;
+}
+
+.sender-create-wizard__stepper {
+    display: flex !important;
+    flex-direction: column !important;
+    min-height: 0 !important;
+    height: 100% !important;
+    overflow: hidden !important;
+}
+
+/* MudStepper internal wrappers must pass height down without scrolling. */
+.sender-create-wizard__stepper .mud-stepper-content,
+.sender-create-wizard__stepper .mud-stepper-nav-content,
+.sender-create-wizard__stepper .mud-stepper-content-wrapper {
+    flex: 1 1 auto !important;
+    min-height: 0 !important;
+    display: flex !important;
+    flex-direction: column !important;
+    overflow: hidden !important;
+}
+
+.sender-create-wizard__step-content,
+.sender-create-wizard__step-layout {
+    flex: 1 1 auto !important;
+    min-height: 0 !important;
+    display: flex !important;
+    flex-direction: column !important;
+}
+
+/* The actual scroll area for every step, mirroring the receiver list behavior. */
+.sender-create-wizard__step-main {
+    flex: 1 1 auto !important;
+    min-height: 0 !important;
+    overflow-y: auto !important;
+    overflow-x: hidden !important;
+    scrollbar-gutter: stable;
+    padding-right: 0.2rem;
 }
 
 .sender-create-wizard-popup .dxbl-popup-footer {
@@ -1543,10 +1615,6 @@
     display: flex;
     flex-direction: column;
     gap: 0.5rem;
-    max-height: min(24vh, 220px);
-    overflow-y: auto;
-    overflow-x: hidden;
-    scrollbar-gutter: stable;
     padding-right: 0.2rem;
 }