test: add comprehensive tests for membership fee UI components

Add tests for all membership fee UI components following TDD principles:

docs/test-status-membership-fee-ui.md

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+# Test Status: Membership Fee UI Components
+
+**Date:** 2025-01-XX  
+**Status:** Tests Written - Implementation Complete
+
+## Übersicht
+
+Alle Tests für die Membership Fee UI-Komponenten wurden geschrieben. Die Tests sind TDD-konform geschrieben und sollten erfolgreich laufen, da die Implementation bereits vorhanden ist.
+
+## Test-Dateien
+
+### Helper Module Tests
+
+**Datei:** `test/mv_web/helpers/membership_fee_helpers_test.exs`
+- ✅ format_currency/1 formats correctly
+- ✅ format_interval/1 formats all interval types
+- ✅ format_cycle_range/2 formats date ranges correctly
+- ✅ get_last_completed_cycle/2 returns correct cycle
+- ✅ get_current_cycle/2 returns correct cycle
+- ✅ status_color/1 returns correct color classes
+- ✅ status_icon/1 returns correct icon names
+
+**Status:** Alle Tests sollten erfolgreich sein (Implementation vorhanden)
+
+**Datei:** `test/mv_web/member_live/index/membership_fee_status_test.exs`
+- ✅ load_cycles_for_members/2 efficiently loads cycles
+- ✅ get_cycle_status_for_member/2 returns correct status
+- ✅ format_cycle_status_badge/1 returns correct badge
+
+**Status:** Alle Tests sollten erfolgreich sein (Implementation vorhanden)
+
+### Member List View Tests
+
+**Datei:** `test/mv_web/member_live/index_membership_fee_status_test.exs`
+- ✅ Status column displays correctly
+- ✅ Shows last completed cycle status by default
+- ✅ Toggle switches to current cycle view
+- ✅ Color coding for paid/unpaid/suspended
+- ✅ Filter "Unpaid in last cycle" works
+- ✅ Filter "Unpaid in current cycle" works
+- ✅ Handles members without cycles gracefully
+- ✅ Loads cycles efficiently without N+1 queries
+
+**Status:** Alle Tests sollten erfolgreich sein (Implementation vorhanden)
+
+### Member Detail View Tests
+
+**Datei:** `test/mv_web/member_live/show_membership_fees_test.exs`
+- ✅ Cycles table displays all cycles
+- ✅ Table columns show correct data
+- ✅ Membership fee type dropdown shows only same-interval types
+- ✅ Warning displayed if different interval selected
+- ✅ Status change actions work (mark as paid/suspended/unpaid)
+- ✅ Cycle regeneration works
+- ✅ Handles members without membership fee type gracefully
+
+**Status:** Alle Tests sollten erfolgreich sein (Implementation vorhanden)
+
+### Membership Fee Types Admin Tests
+
+**Datei:** `test/mv_web/live/membership_fee_type_live/index_test.exs`
+- ✅ List displays all types with correct data
+- ✅ Member count column shows correct count
+- ✅ Create button navigates to form
+- ✅ Edit button per row navigates to edit form
+- ✅ Delete button disabled if type is in use
+- ✅ Delete button works if type is not in use
+- ✅ Only admin can access
+
+**Status:** Alle Tests sollten erfolgreich sein (Implementation vorhanden)
+
+**Datei:** `test/mv_web/live/membership_fee_type_live/form_test.exs`
+- ✅ Create form works
+- ✅ Edit form loads existing type data
+- ✅ Interval field editable on create
+- ✅ Interval field grayed out on edit
+- ✅ Amount change warning displays on edit
+- ✅ Amount change warning shows correct affected member count
+- ✅ Amount change can be confirmed
+- ✅ Amount change can be cancelled
+- ✅ Validation errors display correctly
+- ✅ Only admin can access
+
+**Status:** Alle Tests sollten erfolgreich sein (Implementation vorhanden)
+
+### Member Form Tests
+
+**Datei:** `test/mv_web/member_live/form_membership_fee_type_test.exs`
+- ✅ Membership fee type dropdown displays in form
+- ✅ Shows available types
+- ✅ Filters to same interval types if member has type
+- ✅ Warning displayed if different interval selected
+- ✅ Warning cleared if same interval selected
+- ✅ Form saves with selected membership fee type
+- ✅ New members get default membership fee type
+
+**Status:** Alle Tests sollten erfolgreich sein (Implementation vorhanden)
+
+### Integration Tests
+
+**Datei:** `test/mv_web/member_live/membership_fee_integration_test.exs`
+- ✅ End-to-end: Create type → Assign to member → View cycles → Change status
+- ✅ End-to-end: Change member type → Cycles regenerate
+- ✅ End-to-end: Update settings → New members get default type
+- ✅ End-to-end: Delete cycle → Confirmation → Cycle deleted
+- ✅ End-to-end: Edit cycle amount → Modal → Amount updated
+
+**Status:** Alle Tests sollten erfolgreich sein (Implementation vorhanden)
+
+## Test-Ausführung
+
+Alle Tests können mit folgenden Befehlen ausgeführt werden:
+
+```bash
+# Alle Tests
+mix test
+
+# Nur Membership Fee Tests
+mix test test/mv_web/helpers/membership_fee_helpers_test.exs
+mix test test/mv_web/member_live/
+mix test test/mv_web/live/membership_fee_type_live/
+
+# Mit Coverage
+mix test --cover
+```
+
+## Bekannte Probleme
+
+Keine bekannten Probleme. Alle Tests sollten erfolgreich laufen, da die Implementation bereits vorhanden ist.
+
+## Nächste Schritte
+
+1. ✅ Tests geschrieben
+2. ⏳ Tests ausführen und verifizieren
+3. ⏳ Eventuelle Anpassungen basierend auf Test-Ergebnissen
+4. ⏳ Code-Review durchführen
+