[Studio] Wire consumer page to group APIs

[Aias00]

Summary

• replace the Consumer Group page's static mock data with the shared consumer service/API layer
• load group detail, subscriptions, and consume progress from backend endpoints when opening the detail modal
• wire create, single delete, batch delete, and reset offset actions to API calls with loading/error states
• add page tests covering service-backed list and detail loading

Motivation

This is part of the RocketMQ Studio control-plane baseline/CLIENT-01 work. The page previously rendered static mock consumer data, so a deployed Studio instance could not reflect real Consumer Group state, online instances, subscriptions, or consume progress.

Verification

• npm test -- ConsumerPage.test.tsx consumerGroups.test.ts
• npm run build
• npm run lint (passes with existing Fast Refresh warnings in unrelated files)

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[Aias00]

Superseded by #638. Folded into the consolidated page data loading/state PR to keep Consumer page API wiring with related page-level data loading behavior.