New

• design-system: implement DESIGN.md tokens across dashboard, landing and docs #261
• sub-accounts: add multi-tenant sub-accounts with pooled quotas
• sub-accounts: merge multi-tenant sub-accounts feature

Fixed

• design-system: align dashboard logo color with warm gray-900 #263
• design-system: complete warm palette and add tabular-nums #262
• sdk: remove unused ApiKey import in Rust SDK sub_accounts module
• sub-accounts: add toast notifications and polish dashboard UX
• sub-accounts: correct HTTP status codes and test assertions for sub-account endpoints
• sub-accounts: correct quota SUM type mismatch and register dashboard templates
• sub-accounts: prevent quota race conditions and aggregate analytics auth gap
• sub-accounts: resolve CI lint and compilation issues