[loc] Russian and German localizations added.

[kkkkarim]

Summary

This PR adds internationalization (i18n) infrastructure to the CAVISE documentation using sphinx-intl with gettext. All existing pages have been translated into Russian and German.

Changes

• source/conf.py — added 3 lines for i18n configuration (locale_dirs, gettext_compact, gettext_additional_targets)
• locales/ — new directory containing translation files:
  • ru/LC_MESSAGES/ — 6 .po + 6 .mo files (Russian translations)
  • de/LC_MESSAGES/ — 6 .po + 6 .mo files (German translations)
• Translated 6 pages: index.rst, wiki/index.rst, wiki/install-and-launch.rst, wiki/additional-scripts.rst, wiki/troubleshooting.rst, scenarios/index.rst
• Added build commands for Russian, German, and English documentation
• Defined translation rules: technical terms (CARLA, OpenCDA, SUMO, Docker, etc.) and code blocks remain in English; RST markup is preserved

Validation

• Manual verification (translated docs built successfully for both languages, pages render correctly)

Checklist

• Kept the PR focused and reviewable
• Updated documentation if needed (i18n configuration added)
• Added or updated validation steps if needed (build instructions included)