Update wording across codebase: Replace “Policy/Policies/etc” with “dMRV” (Digital Methodology)

### Problem description

Currently, our codebase, UI, and documentation consistently use the terminology “Policy” or “Policies”. With the latest alignment to product vision and terminology, this is outdated and creates confusion for users and developers.

We need to replace all instances of “Policy/Policies/etc.” with “dMRV” (Digital Methodology) to ensure consistency across the product and documentation.

### Requirements

* Search and update the entire codebase, UI labels, and documentation.
* Replace:
* Policy → dMRV
* Policies → dMRVs (plural usage)
* Ensure database entities, API references, and variable names are updated carefully to avoid breaking changes.
* Update related documentation and comments.
* Ensure no functionality is impacted.

### Definition of done

* All code, UI text, and documentation references updated to “dMRV”/“dMRVs.”
* Database and API naming reviewed to avoid regressions.
* Backward compatibility confirmed (where needed).
* Code passes unit and integration tests.
* Documentation updated.

### Acceptance criteria

* User sees only “dMRV” (or plural form) in UI, not “Policy/Policies.”
* API calls and responses reflect updated terminology (with no breaking changes).
* Developer documentation and inline code comments updated.
* Regression tests confirm functionality remains intact.

**Related**

#2835

#5558