optimize docs localization and validation

[6mm-official]

What changed

• Migrated the documentation to 20 native Fern languages, including native uz, fil, and az translation overlays.
• Removed the old surrogate/standalone locale setup and kept redirects for legacy locale routes.
• Refreshed translation structure, runtime language mappings, SEO metadata, and validation.
• Removed inactive AI Hub pages and duplicate brand archives.
• Pinned the Fern CLI and consolidated project checks.

Why

The locale configuration had drifted between Fern translations, custom standalone routes, runtime mappings, and test fixtures. This update makes all supported languages native Fern locales and adds repeatable validation for publishing.

Impact

• 20 native locales total.
• 87 active pages per locale.
• Existing legacy locale URLs continue to redirect.
• Smaller repository and more reliable local/publish checks.

Validation

• npm ci
• npm run check
• Fern local preview computed all 19 translated locales.
• /uz/home, /fil/home, and /az/home returned HTTP 200 locally.
• Fern validation has no errors; remaining warnings are expected publication-history migration warnings for the three locale-code migrations.