Get the latest opportunities report

**Experimental — the response shape may still change.** The brand's Opportunities report: a prioritized set of ways to get cited more often, with the tracked prompts and cited pages behind each one. The same analysis the dashboard shows, from the same code. Generation is inline and synchronous. A stored report is served while it is fresh and regenerated when it is not, so there is nothing to poll for and no way to be handed a stale one — but a request that triggers a generation waits for it. The freshness window bounds the cost: however many callers ask, one generation per brand per window. There is deliberately no `POST`, which would spend provider budget with nothing metering it per call.

curl -X GET "https://example.com/brands/string/opportunities"

{  "brandId": "string",  "status": "ready",  "generatedAt": "2019-08-24T14:15:22Z",  "model": "string",  "summary": [    "string"  ],  "opportunities": [    {      "category": "creation",      "title": "string",      "why": "string",      "relatedPrompts": [        {          "text": "string",          "promptId": "b5415d63-4390-40ec-8c2b-33a2db2f5c67"        }      ],      "yourCitations": [        {          "url": "http://example.com",          "domain": "string",          "title": "string"        }      ],      "competitorCitations": [        {          "url": "http://example.com",          "domain": "string",          "title": "string"        }      ]    }  ],  "risks": [    "string"  ]}