refactor: rename project from wedding-photo-sharing to PicPeak

- Update Docker image names and network configurations
- Rename package.json project names to picpeak-backend/frontend
- Update CI/CD configurations (Drone CI and GitHub Actions)
- Update documentation and setup scripts
- Update application branding in source code
- Change default database name to picpeak
- Update PM2 ecosystem config

🤖 Generated with [Claude Code](https://claude.ai/code)

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

backend/ecosystem.config.js

@@ -1,6 +1,6 @@
 module.exports = {
   apps: [{
-    name: 'photo-sharing',
+    name: 'picpeak',
     script: './server.js',
     instances: 'max',
     exec_mode: 'cluster',