Add language-aware transliteration for resume filenames

[DaKheera47]

Summary

• Add shared language detection and filename sanitization helpers for supported resume languages
• Use the resolved language when building downloaded resume filenames in Job Page, the orchestrator detail panel, and keyboard shortcuts
• Update Design Resume PDF naming and document the German umlaut mapping in settings docs

Testing

• Added unit coverage for shared transliteration and filename language resolution
• Added UI-level coverage for German filename generation in the Job Page and orchestrator detail panel
• Added server coverage for Design Resume PDF filename generation
• Full orchestrator test suite, Biome, and type checks passed

[DaKheera47]

tested as working