Merged PR 2374: addeding domain layer extrraction

# Summary

This PR introduces a **Case Lifecycle Domain Boundary** to centralize lifecycle decision logic and reduce coupling within the appeals application.

The work is **behaviour-preserving** and introduces no intentional changes to business rules, CRM integrations, translations, dashboards, API routes, or user-facing functionality.

## What was added

New lifecycle boundary:

```text
lib/domain/case-lifecycle/
```

Key responsibilities extracted:

- Specialist process normalization
- Appeal type mapping
- Specialist process stage override mapping
- Stage case-type resolution
- Stage catalogue lookup
- Closed-case status recognition
- Lifecycle stage index resolution
- Lifecycle stage status assignment

## Behaviour preserved

Characterization tests were added before each extraction to preserve:

- Appeal type mapping and aliases
- Specialist process handling
- Lifecycle stage progression
- Closed-case handling
- Status assignment (`complete`, `in-progress`, `not-started`)
- Existing ROW behaviour
- Existing `statuscode` lifecycle semantics

Closed-case recognition remains unchanged for:

```text
1000
5
6
846040013
846040059
846040060
```

## Documentation

Added:

```text
lib/domain/case-lifecycle/README.md
```

Documenting:

- Boundary ownership
- Non-goals
- Lifecycle invariants
- Known architectural constraints
- Future extraction roadmap

## Testing

Added lifecycle characterization coverage for:

- Stage wrapper behaviour
- Specialist process normalization
- Appeal type mapping
- Specialist process stage mapping
- Stage case-type resolution
- Stage catalogue lookup
- Progress behaviour
- Closed-case status handling
- Stage index resolution
- Stage status assignment

## Validation

- Lifecycle characterization tests passed
- `npm run lint` passed with no errors

## Out of Scope

No changes to:

- Stage catalogue ownership
- Representation eligibility
- Dashboard calculations
- CRM/OData queries
- API routes
- Redux state
- EN/CY translations
- Event visibility logic

## Risk

**Low risk**

The refactor was delivered through small, characterization-first slices with no functional changes intended.

Related work items: #23527

components/case/status.js

@@ -4,7 +4,7 @@ import { connect } from "react-redux";
 import useTranslation from "next-translate/useTranslation";
 import { formatDates } from "../utils";
 import { useState } from "react";
-import { getStagesForAppealType } from "./summary/utils/caseStagesByAppealType";
+import { getLifecycleStagesForCase } from "../../lib/domain/case-lifecycle";
 
 const statusClassMap = {
     complete: "govuk-tag govuk-!-margin-top-2",
@@ -29,7 +29,7 @@ const StatusDetails = (props) => {
 
     console.log(props.currentView?.caseReference?.statuscode);
 
-    const stages = getStagesForAppealType(
+    const stages = getLifecycleStagesForCase(
         props.currentView?.caseReference?.appealType,
         props.currentView?.caseReference?.statuscode,
         specialistProcess