Refactor ModelTryContentButton to use useMultiStepNotification

[yomybaby]

Replace the manual notification orchestration in ModelTryContentButton with the useMultiStepNotification hook (FR-2392).

Current Flow (to be replaced)

1. User clicks 'Run this model' → modal.confirm() clone dialog
2. Clone mutation fires → upsertNotification with SSE taskId for clone progress
3. useEffect watches notifications array for clone completion → triggers service creation
4. Service creation → separate upsertNotification with polling Promise

New Flow (multi-step notification)

1. User clicks 'Run this model' → modal.confirm() clone dialog (same)
2. Call start() from useMultiStepNotification with 3 steps:
   • Step 1 (SSE): 'Cloning model folder...' — clone vfolder, returns { taskId }
   • Step 2 (Promise): 'Creating service...' — POST /services with cloned folder ID
   • Step 3 (Promise): 'Waiting for service to be ready...' — poll until active routes
3. On completion: show 'Play your model now!' link to /chat?endpointId=...
4. On failure: show retry button + 'Go to service detail page' link

When already-cloned folder exists

• Steps reduce to Step 2 + Step 3 only (skip clone)

Key Changes

• Remove pendingCloneRef and the useEffect that watches notifications
• Remove createServiceNotificationMsg function
• Add i18n keys: modelService.CloningModelFolder, modelService.CreatingService, modelService.WaitingForServiceReady

Acceptance Criteria

• Unified notification with step progress (clone → create → ready)
• Cancel button works at any step
• Retry works from failed step
• 'Play your model now!' link on completion
• Same behavior for already-cloned folder path (skip clone step)

Dependencies

• FR-2404 (extract shared utilities)
• FR-2392 (useMultiStepNotification — already merged)

Changed Files

• react/src/components/ModelTryContentButton.tsx
• resources/i18n/en.json

JIRA Issue: FR-2405