chore: initialize monorepo with project scaffolding, configs, and CI setup

apps/blockchain-node/src/aitbc_chain/app.py

@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+from contextlib import asynccontextmanager
+
+from fastapi import APIRouter, FastAPI
+from fastapi.responses import PlainTextResponse
+
+from .config import settings
+from .database import init_db
+from .metrics import metrics_registry
+from .rpc.router import router as rpc_router
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    init_db()
+
+def create_app() -> FastAPI:
+    app = FastAPI(title="AITBC Blockchain Node", version="0.1.0", lifespan=lifespan)
+    app.include_router(rpc_router, prefix="/rpc", tags=["rpc"])
+
+    metrics_router = APIRouter()
+
+    @metrics_router.get("/metrics", response_class=PlainTextResponse, tags=["metrics"], summary="Prometheus metrics")
+    async def metrics() -> str:
+        return metrics_registry.render_prometheus()
+
+    app.include_router(metrics_router)
+
+    return app
+
+
+app = create_app()