fix(api): add /api/readyz to authMiddleware bypass list (GRO-2687)

/api/readyz was returning 401 Unauthorized in UAT (GRO-2692 Shedward
regression). The authMiddleware for /api/* did not whitelist /api/readyz,
causing every unauthenticated probe request to be rejected.

Add /api/readyz to the bypass condition alongside /api/auth/* and
/api/health. Add readyz-auth-bypass.test.ts confirming the route passes
through the middleware without auth and that non-whitelisted paths still
block (503 when auth not configured).

Closes GRO-2692 regression (UAT fail).

src/middleware/auth.ts

@@ -23,7 +23,7 @@ if (process.env.AUTH_DISABLED === "true") {
 }
 
 export const authMiddleware: MiddlewareHandler = async (c, next) => {
-  if (c.req.path.startsWith("/api/auth/") || c.req.path === "/api/health") {
+  if (c.req.path.startsWith("/api/auth/") || c.req.path === "/api/health" || c.req.path === "/api/readyz") {
     await next();
     return;
   }