feat: initial Phase 4 backend deployment

- Latest Phase 4 backend code
- JWT authentication with default secret
- PostgreSQL database support
- RESTful API with documentation
- AI-powered features ready

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -1,6 +1,6 @@
 ---
-title: Todo App Backend
-emoji: 📝
+title: Todo Backend - Phase IV
+emoji: 🚀
 colorFrom: blue
 colorTo: purple
 sdk: docker
@@ -10,4 +10,24 @@ pinned: false
 license: mit
 ---
 
-FastAPI backend with AI integration.
+# Todo Backend - Phase IV
+
+FastAPI backend with AI-powered task management.
+
+## Features
+
+- ✅ JWT Authentication
+- ✅ RESTful API
+- ✅ PostgreSQL Database
+- ✅ AI Chatbot Integration
+- ✅ Hybrid NLP Engine
+
+## Environment
+
+Variables configured in Space Settings.
+
+## API Endpoints
+
+- `/health` - Health check
+- `/docs` - Interactive API documentation
+- `/api/` - REST API

src/core/config.py

@@ -24,8 +24,8 @@ class Settings(BaseSettings):
     # Database Configuration
     # ========================================
     database_url: str = Field(
-        default='sqlite:///./todo_app.db',
-        description='Database connection string (defaults to SQLite for HuggingFace Spaces)',
+        default='postgresql+psycopg://todoapp:todoapp_password@localhost:5432/todoapp',
+        description='PostgreSQL connection string',
     )
 
     # ========================================