v2.0.0: Multi-user authentication with JWT

Features:
- User registration and login with JWT tokens
- All data is now user-specific (multi-tenancy)
- Profile page with integrations and logout
- Automatic migration of existing data to first user

Backend changes:
- Added users and refresh_tokens tables
- Added user_id to all data tables (projects, entries, nodes, dictionaries, words, progress, configs, telegram_integrations, weekly_goals)
- JWT authentication middleware
- claimOrphanedData() for data migration

Frontend changes:
- AuthContext for state management
- Login/Register forms
- Profile page (replaced Integrations)
- All API calls use authFetch with Bearer token

Migration notes:
- On first deploy, backend automatically adds user_id columns
- First user to login claims all existing data

play-life-backend/go.mod

@@ -1,11 +1,13 @@
 module play-eng-backend
 
-go 1.21
+go 1.24.0
 
 require (
 	github.com/go-telegram-bot-api/telegram-bot-api/v5 v5.5.1
+	github.com/golang-jwt/jwt/v5 v5.3.0
 	github.com/gorilla/mux v1.8.1
 	github.com/joho/godotenv v1.5.1
 	github.com/lib/pq v1.10.9
 	github.com/robfig/cron/v3 v3.0.1
+	golang.org/x/crypto v0.46.0
 )