ChatWallpaperEditor: wrap loose params in SectionView cards

In ChatInfo > Chat theme screen the wallpaper preset selector, the
wallpaper setup controls, the reset/set-default buttons and the
"Apply to" mode dropdown were rendered as loose composables on a gray
canvas — no card chrome, inconsistent with the rest of Appearance.

Wrap them in SectionView so they read as raised iOS-style cards:
- wallpaper preset selector + setup view → one card
- reset-to-global + set-default buttons → one card
- (advanced mode) Apply-to dropdown → one card
- (collapsed mode) Advanced-settings button → one card

CustomizeThemeColorsSection and ImportExportThemeSection were already
SectionView-wrapped and remain unchanged. UserWallpaperEditor (sister
function with similar layout, lines 28-220) is intentionally left
alone — user reported only the chat-theme entry point.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/views/helpers/ThemeModeEditor.kt

@@ -329,6 +329,7 @@ fun ModalData.ChatWallpaperEditor(
       ThemeManager.currentColors(type, if (type?.sameType(themeModeOverride.value.type) == true) themeModeOverride.value else null, chatModel.currentUser.value?.uiThemes, appPrefs.themeOverrides.get())
     }
 
+    SectionView {
     WallpaperPresetSelector(
       selectedWallpaper = currentTheme.wallpaper.type,
       activeBackgroundColor = currentTheme.wallpaper.background,
@@ -367,9 +368,11 @@ fun ModalData.ChatWallpaperEditor(
       editColor = editColor,
       onTypeChange = onTypeChange,
     )
+    }
 
     SectionSpacer()
 
+    SectionView {
     if (!globalThemeUsed.value) {
       ResetToGlobalThemeButton(remember { chatModel.currentUser }.value?.uiThemes?.preferredMode(isInDarkTheme()) == null) {
         themeModeOverride.value = ThemeManager.defaultActiveTheme(chatModel.currentUser.value?.uiThemes, appPrefs.themeOverrides.get())
@@ -393,6 +396,7 @@ fun ModalData.ChatWallpaperEditor(
         save(themeModeOverride.value.mode, themeModeOverride.value)
       }
     }
+    }
 
     KeyChangeEffect(theme.mode) {
       themeModeOverride.value = theme
@@ -420,6 +424,7 @@ fun ModalData.ChatWallpaperEditor(
         )
       )
       }
+      SectionView {
       ExposedDropDownSettingRow(
         generalGetString(MR.strings.chat_theme_apply_to_mode),
         values,
@@ -435,6 +440,7 @@ fun ModalData.ChatWallpaperEditor(
           }
         }
       )
+      }
 
       SectionDividerSpaced()
 
@@ -448,7 +454,9 @@ fun ModalData.ChatWallpaperEditor(
         }
       }
     } else {
-      AdvancedSettingsButton { showMore = true }
+      SectionView {
+        AdvancedSettingsButton { showMore = true }
+      }
     }
 
     SectionBottomSpacer()