fix(api): use PrismaClientKnownRequestError instanceof, add ConflictException for duplicate routes

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

apps/api/src/modules/routes/routes.service.ts

@@ -1,4 +1,5 @@
-import { BadRequestException, Injectable, NotFoundException } from '@nestjs/common';
+import { BadRequestException, ConflictException, Injectable, NotFoundException } from '@nestjs/common';
+import { Prisma } from '@prisma/client';
 import { PrismaService } from '../../prisma/prisma.service';
 
 const routeInclude = {
@@ -22,17 +23,24 @@ export class RoutesService {
     if (!sourceGroupId || !targetGroupId) {
       throw new BadRequestException('sourceGroupId and targetGroupId are required');
     }
-    return this.prisma.syncRoute.create({
-      data: { sourceGroupId, targetGroupId },
-      include: routeInclude,
-    });
+    try {
+      return await this.prisma.syncRoute.create({
+        data: { sourceGroupId, targetGroupId },
+        include: routeInclude,
+      });
+    } catch (e) {
+      if (e instanceof Prisma.PrismaClientKnownRequestError && e.code === 'P2002') {
+        throw new ConflictException('A route between these groups already exists');
+      }
+      throw e;
+    }
   }
 
   async remove(id: string) {
     try {
       await this.prisma.syncRoute.delete({ where: { id } });
     } catch (e) {
-      if ((e as { code?: string })?.code === 'P2025') {
+      if (e instanceof Prisma.PrismaClientKnownRequestError && e.code === 'P2025') {
         throw new NotFoundException(`Route ${id} not found`);
       }
       throw e;