chore: initial project scaffold and gitignore

app/core/errors.py

@@ -0,0 +1,21 @@
+"""Exception types and FastAPI handlers."""
+
+from fastapi import FastAPI, Request, status
+from fastapi.responses import JSONResponse
+
+
+class PortfolioHubError(Exception):
+    """Base application exception."""
+
+
+class FeatureNotReadyError(PortfolioHubError):
+    """Raised when an endpoint contract exists but the implementation is pending."""
+
+
+def register_exception_handlers(app: FastAPI) -> None:
+    @app.exception_handler(FeatureNotReadyError)
+    async def handle_not_ready(_: Request, exc: FeatureNotReadyError) -> JSONResponse:
+        return JSONResponse(
+            status_code=status.HTTP_501_NOT_IMPLEMENTED,
+            content={"detail": str(exc) or "Feature not implemented yet"},
+        )