fix: improve modal behavior on web and Android scrolling

- Restructure ModalBase to use absolute-positioned backdrop behind card
  content, fixing modal stacking issues on web (React Native Web portals)
- Hide EventOverlay when DeleteEventModal is open to prevent z-index
  conflicts on web
- Add nestedScrollEnabled to CardBase ScrollView for Android
- Use TouchableOpacity with delayPressIn in EventCard for scroll-friendly
  touch handling
- Keep eventToDelete state stable during modal fade-out to prevent
  content flash between recurring/single variants
- Fix German umlauts in DeleteEventModal

CLAUDE.md

@@ -200,6 +200,11 @@ Reusable base components for cards and modals with consistent styling.
 
 ModalBase provides: transparent Modal + backdrop (click-outside-to-close) + Android back button support.
 
+**ModalBase Architecture Note:** Uses absolute-positioned backdrop behind the card content (not nested Pressables). This approach:
+- Fixes modal stacking issues on web (React Native Web renders modals as DOM portals)
+- Allows proper scrolling on Android (no touch event conflicts)
+- Card naturally blocks touches from reaching backdrop due to z-order
+
 **Component Hierarchy:**
 ```
 CardBase
@@ -502,6 +507,7 @@ NODE_ENV=development        # development = pretty logs, production = JSON
   - Supports events from adjacent months visible in grid
   - Uses `useFocusEffect` for automatic reload on tab focus
   - DeleteEventModal integration for recurring event deletion with three modes
+  - EventOverlay hides when DeleteEventModal is open (fixes modal stacking on web)
 - Chat screen fully functional with FlashList, message sending, and event confirm/reject
   - **Multiple event proposals**: AI can propose multiple events in one response
   - Arrow navigation between proposals with "Event X von Y" counter
@@ -515,10 +521,10 @@ NODE_ENV=development        # development = pretty logs, production = JSON
   - keyboardDismissMode="interactive" and keyboardShouldPersistTaps="handled"
 - `EventService`: getAll(), getById(), getByDateRange(), create(), update(), delete(mode, occurrenceDate) - fully implemented with recurring delete modes
 - `ChatService`: sendMessage(), confirmEvent(deleteMode, occurrenceDate), rejectEvent(), getConversations(), getConversation() - fully implemented with cursor pagination and recurring delete support
-- `CardBase`: Reusable card component with header (title/subtitle), content area, and optional footer button - configurable padding, border, text size via props
-- `ModalBase`: Reusable modal wrapper with backdrop, uses CardBase internally - provides click-outside-to-close and Android back button support
+- `CardBase`: Reusable card component with header (title/subtitle), content area, and optional footer button - configurable padding, border, text size via props, ScrollView uses `nestedScrollEnabled` for Android
+- `ModalBase`: Reusable modal wrapper with backdrop (absolute-positioned behind card), uses CardBase internally - provides click-outside-to-close, Android back button support, and proper scrolling on Android
 - `EventCardBase`: Event card with date/time/recurring icons - uses CardBase for structure
-- `EventCard`: Uses EventCardBase + edit/delete buttons for calendar display
+- `EventCard`: Uses EventCardBase + edit/delete buttons (TouchableOpacity with delayPressIn for scroll-friendly touch handling)
 - `ProposedEventCard`: Uses EventCardBase + confirm/reject buttons for chat proposals (supports create/update/delete actions with deleteMode display)
 - `DeleteEventModal`: Delete confirmation modal using ModalBase - shows three options for recurring events (single/future/all), simple confirm for non-recurring
 - `EventOverlay` (in calendar.tsx): Day events overlay using ModalBase - shows EventCards for selected day