[i18n] Complete Hungarian locale

Hungarian was the most incomplete locale (44%). Fill the 1025 missing
keys via LLM translation (6 parallel section-batches, preserving
{placeholders} and plural-segment counts, informal "te" register),
drop 10 stale keys no longer in en.js, and normalise indentation to
2 spaces to match the other locales. hu.json now matches en.js 1:1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: frankrousseau