🐛(y-provider) increase JSON size limits for transcription conversion

Problem:
- Default Express JSON parser limit (100kb) is insufficient for larger
 transcription files
- 2-hour audio transcriptions slightly exceed the 100kb limit, causing request
 failures

Solution:
- Implemented custom middleware to apply different JSON parser configurations
 based on route
- Applied 500kb limit specifically for transcription conversion endpoints
- Maintained default limits for all other routes to preserve security

Technical notes:
- Could not find a built-in Express solution to specify parser config per route
- Custom middleware conditionally applies the appropriate parser configuration

Author: lebaudantoine

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to
 - ✅(frontend) Improve tests coverage
 - ⬆️(docker) upgrade backend image to python 3.13 #973
 - ⬆️(docker) upgrade node images to alpine 3.21
+- 🐛(y-provider) increase JSON size limits for transcription conversion
 
 
 ### Removed

src/frontend/servers/y-provider/__tests__/server.test.ts

@@ -1,5 +1,7 @@
 import request from 'supertest';
 
+import { routes } from '@/routes';
+
 const port = 5557;
 const origin = 'http://localhost:3000';
 
@@ -36,4 +38,34 @@ describe('Server Tests', () => {
       expect(response.body.error).toBe('Forbidden');
     });
   });
+
+  it('should allow JSON payloads up to 500kb for the CONVERT_MARKDOWN route', async () => {
+    const largePayload = 'a'.repeat(400 * 1024); // 400kb payload
+    const response = await request(app)
+      .post(routes.CONVERT_MARKDOWN)
+      .send({ data: largePayload })
+      .set('Content-Type', 'application/json');
+
+    expect(response.status).not.toBe(413);
+  });
+
+  it('should reject JSON payloads larger than 500kb for the CONVERT_MARKDOWN route', async () => {
+    const oversizedPayload = 'a'.repeat(501 * 1024); // 501kb payload
+    const response = await request(app)
+      .post(routes.CONVERT_MARKDOWN)
+      .send({ data: oversizedPayload })
+      .set('Content-Type', 'application/json');
+
+    expect(response.status).toBe(413);
+  });
+
+  it('should use the default JSON limit for other routes', async () => {
+    const largePayload = 'a'.repeat(150 * 1024);
+    const response = await request(app)
+      .post('/some-other-route')
+      .send({ data: largePayload })
+      .set('Content-Type', 'application/json');
+
+    expect(response.status).toBe(413);
+  });
 });

src/frontend/servers/y-provider/src/servers/appServer.ts

@@ -21,7 +21,13 @@ import { logger } from '../utils';
  */
 export const initServer = () => {
   const { app } = expressWebsockets(express());
-  app.use(express.json());
+  app.use((req, res, next) => {
+    if (req.path === routes.CONVERT_MARKDOWN) {
+      // Large transcript files are bigger than the default '100kb' limit
+      return express.json({ limit: '500kb' })(req, res, next);
+    }
+    express.json()(req, res, next);
+  });
   app.use(corsMiddleware);
 
   /**