feat(localization): add multilingual content and per-language publishing

[appsolution-mw]

Pages and CMS entries now share one content identity across languages while each language owns its draft, translated URL, publication state and schedule. Withdrawing the source version leaves independently published translations online; unrelated publishing does not activate offline variants.

• Add language administration, sparse translation inheritance and review, shared visual structure with localized content/visibility, and language-aware Site/Content workspaces and collaboration.
• Publish or schedule selected page/template languages and individual CMS variants. Freeze content, URLs and dependencies; use one live route inventory for HTML, caches, fragments, lists, language switching, canonical/hreflang and sitemaps.
• Carry language context through permissions, preview, plugins, AI/MCP, import/export and public forms. Add non-destructive migration 027 for PostgreSQL and SQLite without changing migrations 001–026 or historical published snapshots.
• Document the lifecycle in docs/features/localization.md and related architecture/feature references.

Validation:

• bun test: 7012 passed, 0 failed; 141299 assertions across 759 files.
• bun run build: passed (TypeScript and production bundle).
• bun run lint: passed.
• git diff --check: passed.
• Real-browser checks with disposable local SQLite data: language setup, source/German authoring and reload, independent page and CMS availability, template publication, translated collection URLs, live language links, canonical/hreflang and sitemap. Local accounts, database, uploads and screenshots are excluded from this PR.