fix: narrow HealthResponse.status to Literal["ok", "degraded"]

Server only ever emits one of these two values (ok when redis+db are
both reachable, degraded when either ping fails). Reference:
apps/api/src/routes/health/index.ts:21 in sgai-api-v2-clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: FrancescoSaverioZuppichini

src/scrapegraph_py/schemas.py

@@ -472,7 +472,7 @@ class CreditsResponse(ResponseModel):
 
 
 class HealthResponse(ResponseModel):
-    status: str
+    status: Literal["ok", "degraded"]
     uptime: int
 
     model_config = ConfigDict(extra="allow")