fix(i18n): check every UI language in the locale consistency tests

[MichaelUray]

Fixes #5048

Problem and change

makeLocalesTest compared only ru against en, so keys missing from (or
left over in) the other twelve shipped languages went unnoticed: about
3000 strings were missing across the asset packages, a few keys had
been translated by name or misspelled, and desktop-preferences had no
Italian file at all.

makeLocalesTest now checks all languages the front end offers and
names the failing language. A package can pass languages that are
known to be incomplete as a skip list; this is used only where the gap
is too large to close here (tracker: 10 languages, controlled-documents:
pt/pt-br, billing: ko, github: no ja file).

The remaining small gaps are closed: missing strings translated,
stale keys removed, misnamed keys renamed (task pt/pt-br, process
pt/pt-br/de, core cs/it, billing cs, communication, login cs) and the
German beta warning moved to the key that is actually used.

Tests

makeLocalesTest now checks all 14 languages; ran all 61 lang.test.ts suites: 61/61 pass. Removing a skip entry makes the corresponding suite fail, so the check is effective.

Notes

• About 180 missing strings were added, misnamed keys (e.g. translated key names in pt/pt-br) renamed, stale keys removed; no removed key is referenced in code.
• Packages with large gaps are listed in per-package skip lists (tracker: 10 languages; controlled-documents: pt, pt-br; billing: ko; github: ja) so CI stays green; the list should only shrink.