feat: add Chunk-Browser tab to RAG page

- New 'Chunk-Browser' tab for sequential chunk browsing
- Qdrant scroll API proxy (scroll + collection-count actions)
- Pagination with prev/next through all chunks in a collection
- Text search filter with highlighting
- Click to expand chunk and see all metadata
- 'In Chunks suchen' button now navigates to Chunk-Browser with correct collection

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

admin-lehrer/app/api/legal-corpus/route.ts

@@ -66,6 +66,72 @@ export async function GET(request: NextRequest) {
         url += `/traceability?chunk_id=${encodeURIComponent(chunkId || '')}&regulation=${encodeURIComponent(regulation || '')}`
         break
       }
+      case 'scroll': {
+        const collection = searchParams.get('collection') || 'bp_compliance_gesetze'
+        const limit = parseInt(searchParams.get('limit') || '20', 10)
+        const offsetParam = searchParams.get('offset')
+        const filterKey = searchParams.get('filter_key')
+        const filterValue = searchParams.get('filter_value')
+        const textSearch = searchParams.get('text_search')
+
+        const scrollBody: Record<string, unknown> = {
+          limit: Math.min(limit, 100),
+          with_payload: true,
+          with_vector: false,
+        }
+        if (offsetParam) {
+          scrollBody.offset = offsetParam
+        }
+        if (filterKey && filterValue) {
+          scrollBody.filter = {
+            must: [{ key: filterKey, match: { value: filterValue } }],
+          }
+        }
+
+        const scrollRes = await fetch(`${QDRANT_URL}/collections/${encodeURIComponent(collection)}/points/scroll`, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify(scrollBody),
+          cache: 'no-store',
+        })
+        if (!scrollRes.ok) {
+          return NextResponse.json({ error: 'Qdrant scroll failed' }, { status: scrollRes.status })
+        }
+        const scrollData = await scrollRes.json()
+        const points = (scrollData.result?.points || []).map((p: { id: string; payload?: Record<string, unknown> }) => ({
+          id: p.id,
+          ...p.payload,
+        }))
+
+        // Client-side text search filter
+        let filtered = points
+        if (textSearch && textSearch.trim()) {
+          const term = textSearch.toLowerCase()
+          filtered = points.filter((p: Record<string, unknown>) => {
+            const text = String(p.text || p.content || p.chunk_text || '')
+            return text.toLowerCase().includes(term)
+          })
+        }
+
+        return NextResponse.json({
+          chunks: filtered,
+          next_offset: scrollData.result?.next_page_offset || null,
+          total_in_page: points.length,
+        })
+      }
+      case 'collection-count': {
+        const col = searchParams.get('collection') || 'bp_compliance_gesetze'
+        const countRes = await fetch(`${QDRANT_URL}/collections/${encodeURIComponent(col)}`, {
+          cache: 'no-store',
+        })
+        if (!countRes.ok) {
+          return NextResponse.json({ count: 0 })
+        }
+        const countData = await countRes.json()
+        return NextResponse.json({
+          count: countData.result?.points_count || 0,
+        })
+      }
       default:
         return NextResponse.json({ error: 'Unknown action' }, { status: 400 })
     }