Backend: regeln.py (Lernregeln zentral), Stats O(n), GET /guides/locks, _norm_titel gehärtet

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/database.py

@@ -216,6 +216,17 @@ async def delete_element(element_id: str) -> bool:
 
 # --- Kapitel-Fortschritt ---
 
+async def list_progress_all() -> dict[str, set[str]]:
+    """Kompletter Kapitel-Fortschritt in einem Query: guide_id → Kapitel-Titel."""
+    db = await get_db()
+    cursor = await db.execute("SELECT guide_id, chapter FROM guide_progress")
+    rows = await cursor.fetchall()
+    out: dict[str, set[str]] = {}
+    for guide_id, chapter in rows:
+        out.setdefault(guide_id, set()).add(chapter)
+    return out
+
+
 async def list_progress(guide_id: str) -> list[str]:
     db = await get_db()
     cursor = await db.execute(