fix: rate-probabilities → European region + stronger browser headers

- preferredRegion: fra1/lhr1/cdg1 to bypass US cloud IP blocks on rateprobability.com
- Better sec-* headers to pass bot detection (same-origin cors mode)
- cache: no-store on fetch to avoid stale null caching
- Log CB count on each invocation for diagnostics

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/rate-probabilities/route.ts

@@ -3,6 +3,7 @@ import { fetchAllCBPaths } from "@/lib/rateprobability";
 import type { RateProbData } from "@/lib/rateprobability";
 
 export const dynamic = "force-dynamic";
+export const preferredRegion = ["fra1", "lhr1", "cdg1"]; // Europe (Frankfurt / London / Paris)
 
 export type { RateProbData, CBRatePath, RateProbMeeting } from "@/lib/rateprobability";
 
@@ -13,8 +14,10 @@ export interface RateProbabilitiesResponse {
 
 export async function GET() {
   const data = await fetchAllCBPaths();
+  const currencies = Object.keys(data);
+  console.log(`[rate-prob] fetched ${currencies.length} CBs: ${currencies.join(", ")}`);
   return NextResponse.json(
     { data, fetchedAt: new Date().toISOString() } satisfies RateProbabilitiesResponse,
-    { headers: { "Cache-Control": "s-maxage=3600, stale-while-revalidate=7200" } }
+    { headers: { "Cache-Control": "no-store" } }
   );
 }