Fix admin template Risk type error and bump version to 1.7.4

[happyloa]

Motivation

• The admin risk table caused a fatal type error on first install because the template used an unqualified Risk type while the model is defined as Watchdog\Models\Risk.
• Preventing this mismatch avoids an E_ERROR on initial page render and improves robustness of the admin UI.
• Version metadata needed to be incremented for the patch release.

Description

• Import the model in the template by adding use Watchdog\Models\Risk; to templates/admin-page.php to ensure the Risk type resolves correctly.
• Bump the plugin version constant in src/Version.php to 1.7.4 and update the plugin header in site-add-on-watchdog.php to 1.7.4.
• Update readme.txt stable tag and add a changelog entry for 1.7.4 describing the fix.

Testing

• No automated tests were executed as part of this change.
• The change is limited to a template import and metadata updates with minimal risk to runtime behavior.
• Files modified: templates/admin-page.php, src/Version.php, site-add-on-watchdog.php, and readme.txt.
• Commit message: Fix admin template Risk type error.

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Codex Task