chore: bump version to 0.15.0

[guima-why]

Summary

• bump the product version from 0.14.0 to 0.15.0
• synchronize Desktop package, Tauri, and Cargo versions
• refresh translation catalog version headers

Validation

• make format (executed; unrelated formatter-only changes were excluded to keep the release PR within the Desktop scope boundary)
• make lint
• make translate
• make test (15,745 passed, 2 skipped)
• uv run python desktop/scripts/scope_audit.py --base origin/main --head HEAD