add-ai-providerlisted

# Add an AI provider The contract lives in `src/lib/ai/provider.ts`: ```ts generateImage({ prompt, userId }): Promise<{ url; width; height; model }>; ``` The default implementation is `src/lib/ai/gateway.ts` (Vercel AI Gateway). Read both files before writing anything. ## Steps 1. **Ask the user first** — a new provider almost always means a new dependency, and dependencies need approval (AGENTS.md). 2. Create `src/lib/ai/<provider>.ts` exporting an object that satisfies the `ImageProvider` interface. Keep it thin: call the API, normalize the response to `{ url, width, height, model }`, throw on failure. 3. Config comes from env. Add the new vars to: - `src/lib/env.ts` (Zod schema, optional unless the provider is active) - `.env.example` (with a comment and a link to where keys come from) 4. Wire selection where the provider is chosen (see how `gateway.ts` and the `AI_MOCK` flag are dispatched) — selection stays env-driven, no provider conditionals in UI or actions. 5. **Do not touch the credits flow.** The generate action already spends before calling the provider and refunds on failure. Your provider just throws on error; the action handles money. 6. Test: unit-test the response normalization with a mocked HTTP layer. Then run the e2e generate flow with the real provider once, manually. ## Scope note This repo intentionally ships one provider. Multi-provider image/video/audio with job queues, auto-refunds and gallery storage is what the