Convert JS files to TS files core directory part 3

### What is this about?

Convert this JS files to TS files
```
app/core/NotificationManager.js
app/core/PreventScreenshot.js
app/core/SecureKeychain.js
app/core/TransactionTypes.js
app/core/Vault.js
```

### Scenario

_No response_

### Design

_No response_

### Technical Details

_No response_

### Threat Modeling Framework

_No response_

### Acceptance Criteria

_No response_

### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

_No response_

Start by reading app/core/NotificationManager.js, PreventScreenshot.js, SecureKeychain.js, TransactionTypes.js, and Vault.js, then compare nearby TypeScript files in app/core to understand the repository's conversion patterns. Done means all five listed core files have been converted to TypeScript and the original JavaScript files are no longer needed.

Written by the indexing model from the issue text.