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.controller.ts

@@ -0,0 +1,23 @@
+import { Body, Controller, Delete, Get, HttpCode, Param, Post, Query } from '@nestjs/common';
+import { RoutesService } from './routes.service';
+
+@Controller('routes')
+export class RoutesController {
+  constructor(private readonly routesService: RoutesService) {}
+
+  @Get()
+  list(@Query('sourceGroupId') sourceGroupId?: string) {
+    return this.routesService.list(sourceGroupId);
+  }
+
+  @Post()
+  create(@Body() body: { sourceGroupId?: string; targetGroupId?: string }) {
+    return this.routesService.create(body.sourceGroupId ?? '', body.targetGroupId ?? '');
+  }
+
+  @Delete(':id')
+  @HttpCode(204)
+  remove(@Param('id') id: string) {
+    return this.routesService.remove(id);
+  }
+}