feat: initial project setup

- FastAPI backend (Python 3.12, uv)
- React 19 + TypeScript + Vite frontend
- Devcontainer with Node 22, Python 3.12, uv, opencode
- Basic app structure and project docs

backend/app/main.py

@@ -0,0 +1,22 @@
+from fastapi import FastAPI
+
+from .settings import settings
+
+app = FastAPI(
+    title="Kirche Einfach API",
+    description="KI-gestützte Verwaltungsplattform für Kirche",
+    version="0.1.0",
+    docs_url="/api/docs",
+    redoc_url="/api/redoc",
+    openapi_url="/api/openapi.json",
+)
+
+
+@app.get("/")
+async def root():
+    return {"message": "Kirche Einfach API", "version": settings.version}
+
+
+@app.get("/health")
+async def health():
+    return {"status": "ok"}