Normalize text domain to site-add-on-watchdog and update hook prefixes

[happyloa]

Motivation

• Standardize the plugin text domain to site-add-on-watchdog (remove -main) so translation functions and the plugin header use a single, valid domain.
• Align admin hooks and filter names to the expected plugin prefix site_add_on_watchdog_ for consistency across code and filters.
• Ensure templates, notices, and generated messages all use the same translation domain to avoid missing translations.
• Keep runtime behavior unchanged other than localization and hook name normalization.

Description

• Replaced occurrences of the old text domain with site-add-on-watchdog across the plugin entry file, PHP sources, and templates (files updated include site-add-on-watchdog.php, src/*.php, and templates/*.php).
• Updated filter/hook names and usages from site_add_on_watchdog_main_* to site_add_on_watchdog_* (for example site_add_on_watchdog_main_admin_history_display -> site_add_on_watchdog_admin_history_display).
• Adjusted __(), _e(), esc_html__(), esc_html_e(), and related localization calls to use the new text domain and updated translator strings in email/notification formatting and admin UI.
• Kept behavior, options, and logic intact while only changing localization strings, plugin header Text Domain, and internal hook/filter identifiers.

Testing

• No automated tests were executed for this change.
• Manual inspection and a project-wide search were used to confirm occurrences of the old text domain and hook prefixes were updated.
• A commit was created containing the updates and the working tree shows the modified files were staged and committed.
• No runtime integration tests were run as part of this PR.

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Codex Task