feat(planner): add remove meal with undo; fix RecipePicker badge for neutral delta

- MealActionSheet: new onremove prop + Entfernen button (guarded by #if)
- +page.svelte: handleRemoveMeal submits delete form, shows undo bar;
  undo re-adds via addSlot form; refactored handleUndo to undoCallback
  pattern; desktop day-detail panel also gets Entfernen button
- RecipePicker: only show green +delta badge when scoreDelta > 0;
  neutral (scoreDelta = 0) shows no badge instead of ⚠ Variationskonflikt
- Tests: page.test.ts remove-meal describe, RecipePicker neutral badge test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/planner/RecipePicker.test.ts

@@ -98,6 +98,14 @@ describe('RecipePicker', () => {
 		expect(screen.getByText(/Keine Treffer/i)).toBeTruthy();
 	});
 
+	it('shows no badge when scoreDelta is zero (neutral, no improvement)', () => {
+		const neutralSuggestions = [
+			{ recipe: { id: 'sn', name: 'Neutrales Rezept', effort: 'easy', cookTimeMin: 20 }, scoreDelta: 0.0, hasConflict: false }
+		];
+		render(RecipePicker, { props: { ...baseProps, suggestions: neutralSuggestions } });
+		expect(screen.queryByTestId('badge-sn')).toBeNull();
+	});
+
 	it('shows loading skeleton instead of Empfohlen section when isLoading is true', () => {
 		render(RecipePicker, { props: { ...baseProps, isLoading: true } });
 		expect(screen.getByTestId('suggestions-loading')).toBeTruthy();