feat: update subject suggestion guidelines and remove obsolete migration

- Enhanced the subject suggestion guidelines to specify that descriptions must not exceed 200 characters.
- Deleted the migration file for adding conversation_id to asignaturas and the associated view, as it is no longer needed.

scripts/generacion_de_tipos_de_supabase.txt

@@ -1,2 +1,5 @@
-Usar --local para generar tipos de la BDD local, y --linked para generar tipos de la BDD remota.
-cmd /c "dx supabase gen types typescript --local > database-types.ts"
+Ejecutar estos dos comandos para la generación de tipos de supabase:
+
+[Console]::OutputEncoding = [System.Text.Encoding]::UTF8
+
+dx supabase gen types typescript --local | Out-File -Encoding utf8 -FilePath "supabase\functions\_shared\database.types.ts"