Replace incorrect Content-Type header with Accept header on bodyless GET proxy fetch calls

[coderabbitai]

Problem

Several Next.js API proxy routes in components/frontend/src/app/api/ send Content-Type: application/json on outbound fetch() calls that use GET with no request body. Content-Type describes the format of a request body; it is semantically incorrect (and misleading) on a bodyless GET. The correct header to signal that the caller expects a JSON response is Accept: application/json.

This was surfaced during review of PR #998 (comment: #998 (comment)). The fix was intentionally deferred from that PR to keep all proxy routes consistent in a single follow-up.

Notably, components/frontend/src/app/api/projects/[name]/agentic-sessions/[sessionName]/agui/events/route.ts already explicitly deletes Content-Type for its GET SSE request, confirming awareness of the issue.

Affected routes (outbound GET fetch with wrong header)

• components/frontend/src/app/api/version/route.ts
• components/frontend/src/app/api/cluster-info/route.ts
• components/frontend/src/app/api/projects/[name]/settings/route.ts (GET handler)
• components/frontend/src/app/api/workflows/ootb/route.ts (GET handler)
• components/frontend/src/app/api/projects/[name]/agentic-sessions/[sessionName]/mcp/status/route.ts

(And any other GET handlers that set Content-Type without a body — a full audit of the components/frontend/src/app/api/ directory is recommended.)

Proposed fix

For each bodyless outbound GET fetch, replace:

headers: {
  'Content-Type': 'application/json',
}

with:

headers: {
  'Accept': 'application/json',
}

Requests that include a body (POST/PUT/PATCH) correctly keep Content-Type: application/json and are out of scope.

References

• PR serve version from backend instead of frontend env var #998
• Comment: serve version from backend instead of frontend env var #998 (comment)
• Requested by: @ktdreyer