[18.0][ADD] project_dms_field: add DMS field for projects

[windweaver828]

Add a DMS field integration for project.project, similar to hr_dms_field.

This module adds a Documents tab on the project form and allows DMS field templates to generate project-specific directory structures.

Included:

• project.project integration with dms.field.mixin
• Project form Documents tab
• Demo DMS template and access group
• Tests covering directory creation, project manager access group updates, and cleanup on unlink

Tested:

• pre-commit run --files project_dms_field/...
• Python syntax check
• XML validation