docs: fix server lookup instructions in publishing guide (#411)

The publishing guide incorrectly suggested users could verify their
server by directly accessing `/servers/{server-name}` or
`/v0/servers/{server-name}`, but the API only supports:

1. **Search by name**: `GET /v0/servers?search={server-name}`
2. **Get by UUID**: `GET /v0/servers/{uuid}`

This PR updates the documentation to show the correct verification
method using the search endpoint.

Fixes #410

docs/reference/api/generic-registry-api.md

@@ -15,7 +15,7 @@ The official registry has some more endpoints and restrictions on top of this. S
 
 ### Core Endpoints
 - **`GET /v0/servers`** - List all servers with pagination
-- **`GET /v0/servers/{id}`** - Get detailed server information by ID  
+- **`GET /v0/servers/{id}`** - Get server details by UUID
 - **`POST /v0/publish`** - Publish new server (optional, registry-specific authentication)
 
 ### Authentication