feat(segments): add DVC source control support

[Copilot]

Prerequisites

• I have read and understood the contributing guide.
• The commit message follows the conventional commits guidelines.
• Tests for the changes have been added (for bug fixes / features).
• Docs have been added/updated (for bug fixes / features).

Description

Adds support for DVC (Data Version Control) as a source control segment.

Implementation:

• New dvc.go segment following existing SCM patterns (Fossil, SVN)
• Detects .dvc directory and parses dvc status -q output
• Tracks file states: added (+), modified (~), deleted (-), missing/not in cache (!)
• Supports status_formats and native_fallback options

Sample configuration:

{
  "type": "dvc",
  "style": "powerline",
  "foreground": "#193549",
  "background": "#945dd6",
  "template": " \ue8d1 {{.Status.String}} "
}

Template properties:

• .Status.Added - new files
• .Status.Modified - modified files
• .Status.Deleted - deleted files
• .Status.Missing - files not in cache
• .Status.String - formatted status string

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Feature request] Add support to dvc source control</issue_title>
<issue_description>### Code of Conduct

• I agree to follow this project's Code of Conduct

What would you like to see added?

Please, add support to dvc source control inside a repo.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature request] Add support to dvc source control #6822

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