feat: complete MongoDB to CouchDB migration

- Migrate Report model to CouchDB with embedded street/user data
- Migrate UserBadge model to CouchDB with badge population
- Update all remaining routes (reports, users, badges, payments) to use CouchDB
- Add CouchDB health check and graceful shutdown to server.js
- Add missing methods to couchdbService (checkConnection, findWithPagination, etc.)
- Update Kubernetes deployment manifests for CouchDB support
- Add comprehensive CouchDB setup documentation

All core functionality now uses CouchDB as primary database while maintaining
MongoDB for backward compatibility during transition period.

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

backend/routes/payments.js

@@ -14,8 +14,7 @@ router.post("/subscribe", auth, async (req, res) => {
       return res.status(404).json({ msg: "User not found" });
     }
 
-    user.isPremium = true;
-    await user.save();
+    await User.update(req.user.id, { isPremium: true });
 
     res.json({ msg: "Subscription successful" });
   } catch (err) {