Set up database configuration and connection management

- Created app/database.py with SQLAlchemy engine, session management, and connection utilities
- Added comprehensive database models in app/models.py for User, Client, Phone, Case, Transaction, Document, and Payment
- Implemented FastAPI application with database lifecycle management in app/main.py
- Added health check endpoint to verify database connectivity
- Created README.md with database configuration documentation
- Verified database connection works correctly with SQLite backend

app/main.py

@@ -1 +1,85 @@
-# FastAPI application entry point
+"""
+FastAPI application entry point for Delphi Database.
+
+This module initializes the FastAPI application, sets up database connections,
+and provides the main application instance.
+"""
+
+import logging
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI, Depends
+from sqlalchemy.orm import Session
+
+from .database import create_tables, get_db, get_database_url
+from .models import User
+
+
+# Configure logging
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """
+    Lifespan context manager for FastAPI application.
+
+    Handles startup and shutdown events:
+    - Creates database tables on startup
+    - Logs database connection info
+    """
+    # Startup
+    logger.info("Starting Delphi Database application...")
+
+    # Create database tables
+    create_tables()
+    logger.info("Database tables created/verified")
+
+    # Log database connection info
+    db_url = get_database_url()
+    logger.info(f"Database connected: {db_url}")
+
+    yield
+
+    # Shutdown
+    logger.info("Shutting down Delphi Database application...")
+
+
+# Create FastAPI application with lifespan management
+app = FastAPI(
+    title="Delphi Database",
+    description="Legal case management database application",
+    version="1.0.0",
+    lifespan=lifespan
+)
+
+
+@app.get("/")
+async def root():
+    """
+    Root endpoint - health check.
+    """
+    return {"message": "Delphi Database API is running"}
+
+
+@app.get("/health")
+async def health_check(db: Session = Depends(get_db)):
+    """
+    Health check endpoint that verifies database connectivity.
+    """
+    try:
+        # Test database connection by querying user count
+        user_count = db.query(User).count()
+        return {
+            "status": "healthy",
+            "database": "connected",
+            "users": user_count
+        }
+    except Exception as e:
+        logger.error(f"Health check failed: {e}")
+        return {
+            "status": "unhealthy",
+            "database": "error",
+            "error": str(e)
+        }