### Check for existing issues

- [x] I have searched the existing issues and checked that my issue is not a duplicate.

### The Feature

Add a way to configure the day on which weekly budgets reset (e.g. `weekly_budget_reset_day`), instead of it being hardcoded to Monday 12am in the timezone set in the LiteLLM config.

Proposed config option (litellm proxy `config.yaml`):

\`\`\`yaml general_settings:     timezone: "US/Pacific"     weekly_budget_reset_day: "sunday" \`\`\`

And/or expose the same setting per-key, per-team, or per-user via the Admin UI (budget settings panel), so different orgs/teams can pick a reset day that suits their primary user base, independent of the proxy-wide `timezone`.

### Motivation, pitch

While using LiteLLM for our company's use-cases, we noticed that the weekly budget reset window is currently fixed to Monday 12am in whatever `timezone` is set in the LiteLLM config, and there's no way to configure the reset day separately.

Example: with `timezone: US/Pacific`, Monday 12am Pacific (PDT) works out to roughly: - Monday ~3am US/Eastern - Monday ~10am UTC - Monday ~3pm China Standard Time (UTC+8) - Monday ~4pm Jap…