[Bug] Task assignment fails when worker names contain non-Latin characters

[rmsonge]

When assigning farm tasks to workers with names containing accents (é, ü) or scripts (中文, العربية), the UI shows "Assignment Failed" without errors in console.

Steps to Reproduce:

1. Create a worker with name "José Fernández".
2. Try assigning a task to this worker.
3. Observe silent failure (HTTP 200 but assignment not saved).

Expected Behavior:

• Task should assign successfully.
• Unicode names should be supported.

Environment:

• Tania Core: v1.6.2
• Database: SQLite
• OS: Ubuntu 22.04

Logs:

{"status":"success"}  // No error despite failure