i18n: services and stores have 12 hardcoded English error/status strings

`src/services/` and `src/stores/` contain user-facing English strings that do not use i18n.

### src/services/comfyRegistryService.ts (7 strings)

HTTP error messages hardcoded:
- 400: "Bad request: Invalid input"
- 401: "Unauthorized: Authentication required"
- 403: "Forbidden: Access denied"
- 404: "Not found: Resource not found"
- 409: "Conflict: Resource conflict"
- 500: "Server error: Internal server error"
- Generic: "Unknown error occurred"

### src/stores/queueStore.ts (5 strings)

Task display status enums:
- "Running", "Pending", "Completed", "Failed", "Cancelled"

### Suggested Fix

1. Move HTTP error messages to i18n keys (e.g. `errors.http.*` namespace)
2. Move task status enums to i18n keys (e.g. `queue.status.*` namespace)
3. These strings are displayed in Queue UI, Toast notifications, and other user-facing areas

Start by reading src/services/comfyRegistryService.ts and src/stores/queueStore.ts, then inspect the existing i18n key conventions used by nearby user-facing strings. Move the listed HTTP errors and task statuses to translation keys, and verify that Queue UI and Toast notifications still display the translated messages.

Written by the indexing model from the issue text.