feat: add React content owner review dashboard

[vystartasv]

Description

Adds a bounded, read-only React Content Owner and Review Assignment Dashboard for SPFx 1.23.2.

What changed

• Reads configured SharePoint lists/libraries with REST GET only.
• Normalizes content owner, reviewer/editor, review date, document status, content type, and safe item-link signals.
• Classifies review dates as overdue, due soon, current, missing, or unknown against a configurable reference date.
• Bounds reads to four sources, five pages, 50 rows per page, and 200 rows per source.
• Validates server-relative paths including spaces, HTTPS web URLs, same-origin links, ports, fragments, traversal, credentials, and unsafe characters.
• Handles malformed rows, missing fields, empty/partial results, access errors, throttling, retry-after, and generic failures.
• Provides responsive accessible table filtering by search, owner, and review status.
• Never assigns owners, creates/updates/deletes review tasks, or alters items, pages, metadata, permissions, or taxonomy.

Validation

• npm ci
• npm test — production-linked tests passed. The SPFx test task emitted one non-fatal generated source-map warning.
• npm run verify — read-only verifier passed before and after packaging.
• npm run build — clean SPFx ship bundle passed without warnings.
• npm run package — production .sppkg passed.
• Metadata, configuration, scope, whitespace, and generated-artifact checks passed.

Tenant validation requested

Please validate representative SharePoint Online lists/libraries with owner and reviewer fields, missing or malformed metadata, overdue/due-soon/current/missing review dates, document statuses, managed paths, spaces in paths, valid and unsafe links, malformed rows, paging bounds, empty results, partial failures, permission denial, throttling, keyboard access, and responsive layout. Real tenant screenshots are welcome; none are fabricated locally.

[vystartasv]

Could someone with a SharePoint Online tenant please validate PR #6494 and add real screenshots if possible?

Please test representative lists/libraries with owner and reviewer fields, missing or malformed metadata, overdue/due-soon/current/missing review dates, document statuses, managed paths, spaces in paths, valid and unsafe links, malformed rows, paging bounds, empty results, partial failures, permission denial, throttling, keyboard access, and responsive layout.

This is a bounded read-only dashboard using SharePoint REST GET requests only. It never assigns owners, creates/updates/deletes review tasks, or alters items, pages, metadata, permissions, or taxonomy. No screenshots are fabricated locally.

[github-actions]

Validation failed!

File: samples/react-content-owner-review-dashboard/assets/sample.json

• Missing 'creationDateTime' property!
• Missing 'updateDateTime' property!

[github-actions]

Sample PR validation for #6494

⚠️ Validation status: warnings

We automatically validate all pull requests against our contribution guidance to ensure that all samples provide a consistent experience to our community.

In order to merge this PR in a timely manner, the following criteria must be met:

Validation	Status
Pull request affects only one folder	✅ Succeeded
Sample folder name follows naming convention	✅ Succeeded
README.md contains visitor stat image	⚠️ Warning
Sample requires a .nvmrc file	⚠️ Warning
Sample requires a README.md	✅ Succeeded
Sample requires a screenshot .png in assets folder	⚠️ Warning
No .sppkg file	✅ Succeeded
No node_modules folder	✅ Succeeded
No lib folder	✅ Succeeded
No upgrade reports	✅ Succeeded

@vystartasv please address the above issues and push new changes to this branch.
For more information, see the contribution guidance.

[github-actions]

Sample PR validation for #6494

⚠️ Validation status: warnings

We automatically validate all pull requests against our contribution guidance to ensure that all samples provide a consistent experience to our community.

In order to merge this PR in a timely manner, the following criteria must be met:

Validation	Status
Pull request affects only one folder	✅ Succeeded
Sample folder name follows naming convention	✅ Succeeded
README.md contains visitor stat image	⚠️ Warning
Sample requires a .nvmrc file	⚠️ Warning
Sample requires a README.md	✅ Succeeded
Sample requires a screenshot .png in assets folder	⚠️ Warning
No .sppkg file	✅ Succeeded
No node_modules folder	✅ Succeeded
No lib folder	✅ Succeeded
No upgrade reports	✅ Succeeded

@vystartasv please address the above issues and push new changes to this branch.
For more information, see the contribution guidance.

[github-actions]

Sample PR validation for #6494

⚠️ Validation status: warnings

We automatically validate all pull requests against our contribution guidance to ensure that all samples provide a consistent experience to our community.

In order to merge this PR in a timely manner, the following criteria must be met:

Validation	Status
Pull request affects only one folder	✅ Succeeded
Sample folder name follows naming convention	✅ Succeeded
README.md contains visitor stat image	✅ Succeeded
Sample requires a .nvmrc file	✅ Succeeded
Sample requires a README.md	✅ Succeeded
Sample requires a screenshot .png in assets folder	⚠️ Warning
No .sppkg file	✅ Succeeded
No node_modules folder	✅ Succeeded
No lib folder	✅ Succeeded
No upgrade reports	✅ Succeeded

@vystartasv please address the above issues and push new changes to this branch.
For more information, see the contribution guidance.