Broken migration: 0018_merge_20251008_1414.py references non-existent 0017_model_status_rocksdb_conversion_and_more

## Problem

Running `python manage.py makemigrations` or `migrate` fails with:

```
django.db.migrations.exceptions.NodeNotFoundError: Migration ifc_validation_models.0018_merge_20251008_1414 dependencies reference nonexistent parent node ('ifc_validation_models', '0017_model_status_rocksdb_conversion_and_more')
```

## Cause

The merge migration `migrations/0018_merge_20251008_1414.py` depends on two `0017` migrations:

1. `0017_add_user_ci_index` — ✅ exists
2. `0017_model_status_rocksdb_conversion_and_more` — ❌ missing

The second migration was never committed or was accidentally deleted. This was introduced in commit `db726dc` ("Add migration").

## Current migrations directory

0016_alter_validationrequest_channel.py
0017_add_user_ci_index.py
0018_merge_20251008_1414.py _**← broken**_
0018_model_status_magic_clamav_alter_validationtask_type.py
0019_alter_validationrequest_file.py

## Steps to reproduce

1. Clone the repository
2. Set up the Django environment
3. Run `python manage.py makemigrations` or `python manage.py migrate`

## Environment

- Django: 5.1.1+
- Python: 3.11

Inspect migrations/0018_merge_20251008_1414.py alongside 0017_add_user_ci_index.py and 0018_model_status_magic_clamav_alter_validationtask_type.py, then review the migration history around commit db726dc. Run python manage.py makemigrations and python manage.py migrate; done means both commands complete without a NodeNotFoundError.

Written by the indexing model from the issue text.