Use test JWT for local environment in post-message

Added the same TEST_AUTHORISATION_JWT used in middleware for local
development to post-message.ts. This ensures authentication works
consistently in local/test environments where x-amzn-oidc-data header
is not present.

Fixes test failures where email parsing was failing due to missing
auth token in local environment.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: gecBurton

frontend/src/pages/post-message.ts

@@ -29,7 +29,13 @@ export async function POST(context: APIContext) {
   }
 
   // get user email from JWT
-  const oidcDataToken = context.request.headers.get('x-amzn-oidc-data') || '';
+  const TEST_AUTHORISATION_JWT = 'eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.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.Pmlltl1M0Q9EAkU96J_zkPJUjjh2TGhQGzfi0v2J-IrxUt1KTnGEcnEk09TUJjdCuyIgO9YEH-uGj5MihnGj6PqCQjq17lWP5YUjYyjgrULfgM6jZ_659RK31wZdRg_72yiy-BeVd-c-v7UzRtdTXIMkwn_aWEIp7own__jfZV_E_32KfelgtwzljVGHjGXdz_Irg6_2B4lbRn8ipWAn3SDlM9Cj8aJw7q5qq7XPk9KkXclivi4bMQJ9RNgMxtgitFtdINRF1A9_pkbERM1LliAgvW-FTLwmVECAGDQyoE8xDQuti8JgixvM22WfpdznSLd2gWAWMiyYZJwRxzFSVw'; // pragma: allowlist secret
+  let oidcDataToken;
+  if (process.env.ENVIRONMENT === 'local') {
+    oidcDataToken = TEST_AUTHORISATION_JWT;
+  } else {
+    oidcDataToken = context.request.headers.get('x-amzn-oidc-data') || '';
+  }
   console.log('OIDC data token present:', !!oidcDataToken, 'length:', oidcDataToken.length);
   const authResult = await parseAuthToken(oidcDataToken);
   const userEmail = authResult.email;