## Problem
The Backups & Restore feature was added in the `2025-04` API, and needs
to be implemented in the client.

Documentation:
https://docs.pinecone.io/guides/manage-data/backups-overview

## Solution
Backups and Restore functionality adds a number of new operations /
methods under the Pinecone class.

Add new action functions and unit tests for the following:
- `createBackup`
- `createIndexFromBackup`
- `describeBackup`
- `describeRestoreJob`
- `listBackups`
- `listRestoreJobs`
- `deleteBackup`

This PR also updates the `README` to include documentation around the
feature, along with doc comments inline for all new methods, types, etc.

We skipped integration tests for this feature for the moment since it
can take some time for a restoration job to complete. I've added
detailed unit test coverage for basic piping between the interface and
underlying OpenAPI internals, plus validation and error handling.

I've also done a fair bit of manual testing which I'll share below:

```
> await client.createBackup({ indexName: 'local-utility-index', name: 'my-backup', description: 'this is my backup' })
{
  backupId: '3df86526-0edf-41b0-a555-513effa2146d',
  sourceIndexName: 'local-utility-index',
  sourceIndexId: '1d18673a-ed0e-4cdc-946f-541560367abf',
  name: 'my-backup',
  description: 'this is my backup',
  status: 'Initializing',
  cloud: 'aws',
  region: 'us-east-1',
  dimension: undefined,
  metric: undefined,
  recordCount: undefined,
  namespaceCount: undefined,
  sizeBytes: undefined,
  tags: {},
  createdAt: '2025-05-08T14:52:00.236917882Z'
}

> await client.describeBackup('3df86526-0edf-41b0-a555-513effa2146d')
{
  backupId: '3df86526-0edf-41b0-a555-513effa2146d',
  sourceIndexName: 'local-utility-index',
  sourceIndexId: '1d18673a-ed0e-4cdc-946f-541560367abf',
  name: 'my-backup',
  description: 'this is my backup',
  status: 'Ready',
  cloud: 'aws',
  region: 'us-east-1',
  dimension: 5,
  metric: undefined,
  recordCount: 0,
  namespaceCount: 2,
  sizeBytes: 66877,
  tags: {},
  createdAt: '2025-05-08T14:52:00.236989Z'
}

> await client.listBackups()
{
  data: [
    {
      backupId: '3df86526-0edf-41b0-a555-513effa2146d',
      sourceIndexName: 'local-utility-index',
      sourceIndexId: '1d18673a-ed0e-4cdc-946f-541560367abf',
      name: 'my-backup',
      description: 'this is my backup',
      status: 'Ready',
      cloud: 'aws',
      region: 'us-east-1',
      dimension: 5,
      metric: undefined,
      recordCount: 0,
      namespaceCount: 2,
      sizeBytes: 66877,
      tags: {},
      createdAt: '2025-05-08T14:52:00.236989Z'
    },
    ...
  ],
  pagination: undefined
}

> await client.createIndexFromBackup({ backupId: '11450b9f-96e5-47e5-9186-03f346b1f385', name: 'my-restored-index' })
{
  restoreJobId: '3de68445-77bf-4a74-9790-440523b5213b',
  indexId: '8987dd9f-f3e4-49a3-bbd2-3d73cb9c2810'
}

> await client.listRestoreJobs()
{
  data: [
    {
      restoreJobId: '3de68445-77bf-4a74-9790-440523b5213b',
      backupId: '11450b9f-96e5-47e5-9186-03f346b1f385',
      targetIndexName: 'my-restored-index',
      targetIndexId: '8987dd9f-f3e4-49a3-bbd2-3d73cb9c2810',
      status: 'Pending',
      createdAt: 2025-05-08T14:55:12.749Z,
      completedAt: undefined,
      percentComplete: undefined
    },
    ...
  ],
  pagination: undefined
}
```


## Type of Change
- [ ] Bug fix (non-breaking change which fixes an issue)
- [X] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update
- [ ] Infrastructure change (CI configs, etc)
- [ ] Non-code change (docs, etc)
- [ ] None of the above: (explain here)

## Test Plan

CI - external app test, integration tests, unit tests

For manual testing, you can pull this branch down and run things locally
with `npm run repl`. Set your `PINECONE_API_KEY` as an env variable, and
then run the following:

From the top level of the `pinecone-ts-client` repo:
```bash
# this utility creates a new index and seeds some namespaces with data
npx tsx ./utils/generateAndSeedIndex.ts

npm run repl
await init()

await client.createBackup({ indexName: 'local-utility-index' })
await client.describeBackup('backup-id')
await client.listBackups()
await client.createIndexFromBackup({ backupId: 'backup-id' })
# etc
```



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