chore(i18n): regenerate translation catalogs with wp i18n tooling

[katsar0v]

Summary

Regenerates the translation catalogs with the official WP-CLI i18n tooling instead of hand edits, as a follow-up to #127:

• mail-system.pot regenerated with wp i18n make-pot — source references now carry exact file:line numbers and entries follow source order, so future regenerations produce minimal, deterministic diffs.
• bg_BG.po / de_DE.po synced with wp i18n update-po.
• .mo files recompiled with wp i18n make-mo (composer translations).

What changed in the catalogs

• No translated string was modified or removed — verified by diffing msgid/msgstr pairs against main.
• 38 stale msgids (strings no longer present in any gettext call in the code) were dropped.
• Strings that exist in the code but were missing from the catalogs (e.g. database-repair notices) were added as untranslated entries — they rendered in English before and still do, but are now visible to translators.
• All 20 context-qualified status entries from fix(i18n): correct Bulgarian grammar for status labels #127 are preserved with translations intact.

Verification

• php vendor/bin/phpunit -c tests/phpunit.xml — 274 passing (includes StatusTranslationsTest, which asserts every _x() context in the source is present and translated in all three catalogs)
• composer phpcs — clean
• .mo output matches wp i18n make-mo byte-for-byte (Translations workflow check)

🤖 Generated with Claude Code