fix(import+screening): GET-Alias, DELETE-Endpoint, ehrlicher Scan-Status

Import-Backend:
- GET /v1/import (Root-Alias) → list_documents; behebt URL-Mismatch im Proxy
- DELETE /v1/import/{document_id} → löscht Dokument + Gap-Analyse (mit Tenant-Isolierung)
- 6 neue Tests (65 total, alle grün)

Screening-Frontend:
- Simulierten Fortschrittsbalken (Math.random) entfernt — war inhaltlich falsch
- Ersetzt durch indeterminate Spinner + rotierende ehrliche Status-Texte
  (z.B. "OSV.dev Datenbank wird abgefragt...") im 2-Sek.-Takt
- Kein scanProgress-State mehr benötigt

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

backend-compliance/compliance/api/import_routes.py

@@ -400,3 +400,46 @@ async def list_documents(tenant_id: str = "default"):
         return DocumentListResponse(documents=documents, total=len(documents))
     finally:
         db.close()
+
+
+@router.get("", response_model=DocumentListResponse)
+async def list_documents_root(
+    tenant_id: str = "default",
+    x_tenant_id: Optional[str] = Header(None, alias="X-Tenant-ID"),
+):
+    """Alias: GET /v1/import → list documents (proxy-compatible URL)."""
+    tid = x_tenant_id or tenant_id
+    return await list_documents(tenant_id=tid)
+
+
+@router.delete("/{document_id}")
+async def delete_document(
+    document_id: str,
+    tenant_id: str = "default",
+    x_tenant_id: Optional[str] = Header(None, alias="X-Tenant-ID"),
+):
+    """Delete an imported document and its gap analysis."""
+    tid = x_tenant_id or tenant_id
+    db = SessionLocal()
+    try:
+        # Delete gap analysis first (FK dependency)
+        db.execute(
+            "DELETE FROM compliance_gap_analyses WHERE document_id = :doc_id AND tenant_id = :tid",
+            {"doc_id": document_id, "tid": tid},
+        )
+        result = db.execute(
+            "DELETE FROM compliance_imported_documents WHERE id = :doc_id AND tenant_id = :tid",
+            {"doc_id": document_id, "tid": tid},
+        )
+        db.commit()
+        if result.rowcount == 0:
+            raise HTTPException(status_code=404, detail="Document not found")
+        return {"success": True, "deleted_id": document_id}
+    except HTTPException:
+        raise
+    except Exception as e:
+        db.rollback()
+        logger.error(f"Failed to delete document {document_id}: {e}")
+        raise HTTPException(status_code=500, detail="Failed to delete document")
+    finally:
+        db.close()