fix(billing): Prevent crash on invalid data category for plan

[volokluev]

The billing overview page (/settings/billing/overview/) was crashing when the getBucket function encountered a data category that didn't have a corresponding bucket in the plan's configuration.

This could happen when:

• A plan has an unexpected or newly added data category (e.g., seer_user)
• The plan's bucket configuration is incomplete or mismatched

Changes:

• Modified getBucket to report errors to Sentry with full context (buckets, events, price, shouldMinimize)
• Returns a fallback bucket with zero price instead of throwing an error
• The page now continues to render instead of crashing

Impact:

• Users no longer experience crashes on the billing page
• We still get error reports in Sentry to investigate which data categories are causing issues
• The affected product row displays with $0 additional spend (a safe fallback)

This maintains observability while providing a better user experience.