Initial commit: Backend API Phase 1a complete

- FastAPI backend with JWT auth
- PostgreSQL database schema
- Trees and Sessions CRUD APIs
- Export functionality (Markdown, Text, HTML)
- Docker setup for local development
- Alembic migrations

backend/app/main.py

@@ -0,0 +1,57 @@
+from contextlib import asynccontextmanager
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from app.core.config import settings
+from app.core.database import init_db
+from app.api.router import api_router
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """Application lifespan handler."""
+    # Startup
+    # Note: In production, use Alembic migrations instead of init_db
+    # await init_db()
+    yield
+    # Shutdown
+    pass
+
+
+app = FastAPI(
+    title=settings.APP_NAME,
+    description="A troubleshooting decision tree application for MSP engineers",
+    version="1.0.0",
+    docs_url="/api/docs",
+    redoc_url="/api/redoc",
+    openapi_url="/api/openapi.json",
+    lifespan=lifespan
+)
+
+# Configure CORS
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=settings.CORS_ORIGINS,
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Include API router
+app.include_router(api_router, prefix=settings.API_V1_PREFIX)
+
+
+@app.get("/")
+async def root():
+    """Root endpoint."""
+    return {
+        "message": "Troubleshooting Decision Tree API",
+        "docs": "/api/docs",
+        "version": "1.0.0"
+    }
+
+
+@app.get("/health")
+async def health_check():
+    """Health check endpoint."""
+    return {"status": "healthy"}