fix: Rezeptverlauf-Bilder lokal speichern und Windows-Subprocess-Fix

- Bilder beim Extrahieren lokal cachen (data/images/{id}.ext) und über GET /api/history/{id}/image ausliefern; Löschen bei Verlaufseintrag-Entfernung
- history.db in ./data/ Volume verschoben, damit sie Container-Rebuilds überlebt
- yt-dlp Subprocess-Aufrufe auf Windows gefixt: run_in_executor statt asyncio.create_subprocess_exec (SelectorEventLoop-Kompatibilität)
- ./data:/app/data Docker-Volume für persistente Datenhaltung hinzugefügt

app/api/history.py

@@ -1,6 +1,8 @@
-"""GET /api/history, DELETE /api/history/{id}"""
+"""GET /api/history, DELETE /api/history/{id}, GET /api/history/{id}/image"""
 from fastapi import APIRouter, HTTPException
+from fastapi.responses import FileResponse
 from app.services.history_service import get_all, delete_recipe
+from app.services import image_service
 
 router = APIRouter()
 
@@ -13,8 +15,21 @@ async def get_history():
         raise HTTPException(status_code=500, detail=str(e))
 
 
+@router.get("/history/{history_id}/image")
+async def get_history_image(history_id: int):
+    path = image_service.find_cached_image(history_id)
+    if path is None:
+        raise HTTPException(status_code=404, detail="No cached image")
+    ext_to_mime = {v: k for k, v in image_service.MIME_TO_EXT.items()}
+    media_type = ext_to_mime.get(path.suffix.lstrip("."), "image/jpeg")
+    return FileResponse(path, media_type=media_type)
+
+
 @router.delete("/history/{history_id}")
 async def delete_history_entry(history_id: int):
+    cached = image_service.find_cached_image(history_id)
+    if cached:
+        cached.unlink(missing_ok=True)
     try:
         delete_recipe(history_id)
         return {"status": "ok"}