Restructure: Move 52 files into 7 domain packages

korrektur/ zeugnis/ admin/ compliance/ worksheet/ training/ metrics/
52 shims, relative imports, RAG untouched.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

klausur-service/backend/worksheet/nru_generator.py

@@ -0,0 +1,26 @@
+"""
+NRU Worksheet Generator — barrel re-export.
+
+All implementation split into:
+  nru_worksheet_models — data classes, entry separation
+  nru_worksheet_html   — HTML generation
+  nru_worksheet_pdf    — PDF generation
+
+Per scanned page, we generate 2 worksheet pages.
+"""
+
+# Models
+from .nru_models import (  # noqa: F401
+    VocabEntry,
+    SentenceEntry,
+    separate_vocab_and_sentences,
+)
+
+# HTML generation
+from .nru_html import (  # noqa: F401
+    generate_nru_html,
+    generate_nru_worksheet_html,
+)
+
+# PDF generation
+from .nru_pdf import generate_nru_pdf  # noqa: F401