Fix generated Sphinx docs build

[Shizoqua]

Description

Fixes #5592 by making docs generated with kedro new --tools=docs build API docs without requiring users to manually discover or run sphinx-apidoc.

Development notes

• Added generated project docs/Makefile and docs/make.bat.
• Updated the generated docs html target to run sphinx-apidoc before sphinx-build, which creates docs/source/modules.rst.
• Kept the existing modules toctree reference in docs/source/index.rst.
• Updated generated Sphinx conf.py to include the project src path for autodoc imports.
• Added starter template test coverage and updated the expected docs-tool file count.

Tested with:

• python -m pytest --no-cov tests/framework/cli/starters -q
299 passed
• Generated a project with kedro new --tools docs --example no
• Ran generated docs/make.bat html
• Confirmed docs/source/modules.rst and docs/build/html/index.html were created.

Developer Certificate of Origin

All commits are signed off with Signed-off-by.

Checklist

• Read the [contributing](https://github.com/kedro-org/kedro/blob/main/CONTRIBUTING.md) guidelines
• Signed off each commit with a [Developer Certificate of Origin (DCO)](https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/managing-repository-settings/managing-the-commit-signoff-policy-for-your-repository)
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the [RELEASE.md](https://github.com/kedro-org/kedro/blob/main/RELEASE.md) file
• Added tests to cover my changes
• Checked if this change will affect Kedro-Viz, and if so, communicated that with the Viz team