Move cncf/project-template ownership to TOC Project Reviews Subproject

## Proposal

Transfer ownership of [cncf/project-template](https://github.com/cncf/project-template) from TAG Contributor Strategy to the **TOC Project Reviews Subproject**, and move the template content into the `cncf/toc` repository.

## Why

The project-template repo contains governance, maintainer, contributor ladder, and security templates that are directly referenced by:
- TOC DD triage and evaluation processes
- Incubation and graduation application templates
- The governance best practices document ([PR #2224](https://github.com/cncf/toc/pull/2224))

These templates are consumed by the TOC during due diligence, not by TAG Contributor Strategy during project onboarding. The Project Reviews Subproject already reviews governance and technical artifacts — owning the templates they reference is a natural fit.

TAG Contributor Strategy's charter has evolved with the TAG restructuring. The project-template repo should align with the group that actively maintains and references these templates in the DD process.

Consolidating the templates into `cncf/toc` eliminates the indirection of referencing a separate repo and ensures template updates go through the same review process as the DD checklist and application templates they support.

## Requested Changes

1. **Move template content into `cncf/toc`** — add `GOVERNANCE.md`, `GOVERNANCE-subprojects.md`, `GOVERNANCE-elections.md`, `GOVERNANCE-maintainer.md`, `CONTRIBUTOR_LADDER.md`, `CONTRIBUTING.md`, `MAINTAINERS.md`, `REVIEWING.md`, `DESIGN-PROPOSALS.md`, and `README-template.md` under a `templates/project-template/` directory (or similar) in `cncf/toc`

2. **Update CODEOWNERS** to include:
- TOC members
- CNCF projects staff
- Project Reviews Subproject members

3. **Update references** in DD application templates, dd-toc-guide, and governance review template to point to the new location in `cncf/toc`

4. **Archive `cncf/project-template`** with a README redirect pointing to the new location in `cncf/toc`

5. **Update any references** in TAG Contributor Strategy docs that point to project-template as their responsibility

## Related

- [Project Reviews Subproject](https://github.com/cncf/toc/tree/main/toc_subprojects/project-reviews-subproject)
- [Governance best practices PR #2224](https://github.com/cncf/toc/pull/2224) — references these templates
- [Template updates PR #50](https://github.com/cncf/project-template/pull/50) — active updates to templates
- [Post-graduation health check PR #2225](https://github.com/cncf/toc/pull/2225) — uses template patterns
- [CloudNativePG governance proposal](https://github.com/cncf/toc-private/pull/206) — recommended `GOVERNANCE-subprojects.md` template to a project during DD