Point the v2 client at https://api.fastfuels.silvxlabs.com/v2

[amarcozzi]

Summary

When the API moves behind the load balancer (silvxlabs/FastFuels-IaC#1), the v2 API becomes available at https://api.fastfuels.silvxlabs.com/v2. Update the v2 client to use it.

Changes

• fastfuels_sdk/v2/client_library/base_url.py: DEFAULT_BASE_URL → https://api.fastfuels.silvxlabs.com/v2 (currently the raw run.app URL)
• Update generate_client.sh so regeneration records the new URL
• Release

Coordination

Hard cutover — release together with the v2 API gaining its /v2 path prefix and the LB DNS cutover. Old SDK versions pointing at run.app root paths stop working once the prefix deploys; the lockdown issue (silvxlabs/FastFuels-IaC#2) later closes run.app entirely.

The v1 client is unaffected (already targets https://api.fastfuels.silvxlabs.com with /v1 paths).