cucumber/applications: indexer-backed box query steps are missing

[manuelmauro]

Symptom

After #265 added the `an indexer v2 client` step, the `applications.feature` background no longer fails outright — but the box-query scenarios at the end of each outline still skip because several step phrases are undefined.

Reported by cucumber as `?` (undefined) on lines like:

```gherkin
according to "indexer", with 0 being the parameter that limits results, the current application should have 3 boxes.
according to indexer, with 1 being the parameter that limits results, and "b64:APj/IA==" being the parameter that sets the next result, the current application should have the following boxes "MTE0NTE0".
```

The corresponding `algod`-backed phrases are wired (the algod box query step exists in `applications.rs`); the indexer variants are not.

Reproduction

1. `./test-harness.sh up`
2. `cargo test --test features_runner --`
3. `applications.feature` skips at the indexer box assertions after a successful app create / opt-in.

Acceptance

• Step defs for the `according to "indexer"` family of box queries, mirroring the algod variants. They should delegate to `Indexer::lookup_application_box_by_id_and_name` and `Indexer::search_for_application_boxes`
• `applications.feature` runs green
• No `?` (undefined) steps in the cucumber output

Related

Same flow needs the indexer to be caught up before the assertions — see the step `I wait for indexer to catch up to the round where my most recent transaction was confirmed.` which is also undefined.