Fix SSE routing: exclude text/event-stream requests from API rewrite

afterFiles ordering was insufficient in Next.js 14 — the catch-all
/api/v1/* rewrite still intercepted SSE requests before route handlers.

Fix: add a `missing` condition on `Accept: text/event-stream` to the
rewrite rule. EventSource always sends this header, so SSE requests now
skip the rewrite entirely and are handled by the existing route handlers
(app/api/v1/ppt/outlines/stream, presentation/stream, jobs/stream).
Normal JSON API requests are unaffected.

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

frontend/next.config.mjs

@@ -7,29 +7,29 @@ const nextConfig = {
 
 
   // Proxy API and static asset requests to FastAPI backend.
-  // afterFiles: Next.js checks route handlers first; only falls through to
-  // these rewrites if no matching app/api/ route handler exists.
-  // This ensures SSE route handlers (outlines/stream, presentation/stream, etc.)
-  // are served directly without being intercepted by the catch-all /api/v1/* rewrite.
+  //
+  // The /api/v1/* rewrite uses a `missing` condition on the Accept header so
+  // it does NOT match SSE requests (EventSource always sends Accept: text/event-stream).
+  // SSE paths have explicit route handlers in app/api/v1/*/stream/[id]/route.ts
+  // that stream events properly. Normal JSON requests go through the rewrite as before.
   async rewrites() {
-    return {
-      beforeFiles: [],
-      afterFiles: [
-        {
-          source: '/api/v1/:path*',
-          destination: `${API_URL}/api/v1/:path*`,
-        },
-        {
-          source: '/app_data/:path*',
-          destination: `${API_URL}/app_data/:path*`,
-        },
-        {
-          source: '/static/:path*',
-          destination: `${API_URL}/static/:path*`,
-        },
-      ],
-      fallback: [],
-    };
+    return [
+      {
+        source: '/api/v1/:path*',
+        missing: [
+          { type: 'header', key: 'accept', value: 'text/event-stream' },
+        ],
+        destination: `${API_URL}/api/v1/:path*`,
+      },
+      {
+        source: '/app_data/:path*',
+        destination: `${API_URL}/app_data/:path*`,
+      },
+      {
+        source: '/static/:path*',
+        destination: `${API_URL}/static/:path*`,
+      },
+    ];
   },
 
   images: {