Wiring: imagePreviewStore filename mismatch + CreditTopUpOption orphaned

## Recommendation

### 🔧 FIX: Rename mismatched store file and remove orphaned component

## What Was Found

### imagePreviewStore.ts — Filename/Export Mismatch
- `src/stores/imagePreviewStore.ts` exports `useNodeOutputStore` with `defineStore('nodeOutput')`
- All 15+ consumers import `useNodeOutputStore` from `@/stores/imagePreviewStore`
- The file should be renamed to `nodeOutputStore.ts` to match its export

### CreditTopUpOption.vue — Orphaned Component
- `src/components/dialog/content/credit/CreditTopUpOption.vue`
- Never imported or used in any `.vue` or `.ts` file
- Only reference is its own `.test.ts` file
- Likely left behind after a credit UI refactor

## Context

The store rename is a 5-minute fix. The orphaned component can be safely deleted (verify no external consumers first).

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**Category:** Wiring Gap | **Confidence:** HIGH | **Tools:** Semantic analysis
_Filed by audit-code skill_

Part of #11022

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-11045-Wiring-imagePreviewStore-filename-mismatch-CreditTopUpOption-orphaned-33e6d73d36508147a733cf26dd9c8a65) by [Unito](https://www.unito.io)