refactor(search): extract ChipType to chip-types.ts; audit NL fixtures

Pre-implementation step for #743: ChipType union extracted from
InterpretationChipRow and +page.svelte into shared chip-types.ts;
resolvedTags/tagsApplied neutral defaults added to test fixtures.

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

frontend/e2e/nl-search.spec.ts

@@ -13,8 +13,10 @@ const interpretation = {
 	dateFrom: '1914-01-01',
 	dateTo: '1918-12-31',
 	keywords: ['krieg'],
+	resolvedTags: [{ id: '33333333-3333-3333-3333-333333333333', name: 'Weltkrieg', color: 'sage' }],
 	rawQuery: 'Was hat Walter an Emma im Krieg geschrieben?',
-	keywordsApplied: true
+	keywordsApplied: true,
+	tagsApplied: true
 };
 
 const nlResponse = {