🐛(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

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