feat(api): add RoutesModule with GET/POST/DELETE /routes endpoints

Implements RoutesService and RoutesController for SyncRoute CRUD, wires
GroupsModule and RoutesModule into AppModule; 11 new tests, all 31 pass.

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

@@ -0,0 +1,41 @@
+import { BadRequestException, Injectable, NotFoundException } from '@nestjs/common';
+import { PrismaService } from '../../prisma/prisma.service';
+
+const routeInclude = {
+  sourceGroup: { select: { name: true } },
+  targetGroup: { select: { name: true } },
+} as const;
+
+@Injectable()
+export class RoutesService {
+  constructor(private readonly prisma: PrismaService) {}
+
+  list(sourceGroupId?: string) {
+    return this.prisma.syncRoute.findMany({
+      where: sourceGroupId ? { sourceGroupId } : undefined,
+      include: routeInclude,
+      orderBy: { createdAt: 'desc' },
+    });
+  }
+
+  async create(sourceGroupId: string, targetGroupId: string) {
+    if (!sourceGroupId || !targetGroupId) {
+      throw new BadRequestException('sourceGroupId and targetGroupId are required');
+    }
+    return this.prisma.syncRoute.create({
+      data: { sourceGroupId, targetGroupId },
+      include: routeInclude,
+    });
+  }
+
+  async remove(id: string) {
+    try {
+      await this.prisma.syncRoute.delete({ where: { id } });
+    } catch (e) {
+      if ((e as { code?: string })?.code === 'P2025') {
+        throw new NotFoundException(`Route ${id} not found`);
+      }
+      throw e;
+    }
+  }
+}