fix(api): inscription parent — body 15mb, uploads persistants, 409 si unique PG

- NestExpressApplication + useBodyParser json/urlencoded 15mb
- UPLOAD_PHOTOS_DIR: résolution chemin absolu/relatif + doc .env.example / proxy
- docker-compose: volume backend_uploads + UPLOAD_PHOTOS_DIR par défaut
- Map erreur PostgreSQL 23505 → ConflictException (parent + AM)
- Logs Nest si échec SMTP après inscription (email déjà géré)

Made-with: Cursor

backend/src/main.ts

@@ -1,4 +1,5 @@
 import { NestFactory } from '@nestjs/core';
+import { NestExpressApplication } from '@nestjs/platform-express';
 import { AppModule } from './app.module';
 import { ConfigService } from '@nestjs/config';
 import { SwaggerModule } from '@nestjs/swagger/dist/swagger-module';
@@ -7,8 +8,13 @@ import { ValidationPipe } from '@nestjs/common';
 import { LogRequestInterceptor } from './common/interceptors/log-request.interceptor';
 
 async function bootstrap() {
-  const app = await NestFactory.create(AppModule,
-    { logger: ['error', 'warn', 'log', 'debug', 'verbose'] });
+  const app = await NestFactory.create<NestExpressApplication>(AppModule, {
+    logger: ['error', 'warn', 'log', 'debug', 'verbose'],
+  });
+
+  // Photos inscription (base64) : limite Express par défaut ~100 ko → 413/500 sans ceci
+  app.useBodyParser('json', { limit: '15mb' });
+  app.useBodyParser('urlencoded', { extended: true, limit: '15mb' });
 
   // Log de chaque appel API si LOG_API_REQUESTS=true (mode debug)
   app.useGlobalInterceptors(new LogRequestInterceptor());