This commit introduces the initial implementation of the input handler and Pydantic data models.
- Adds `src/modules/input_handler.py` with text normalization and stubs for other input types.
- Adds `src/data_models.py` with `RawInput`, `ExtractedExpense`, `ProvisionalExpense`, and `FinalExpense` models.
- Integrates the new modules into the `/process-expense` endpoint in `src/main.py`.
- Updates `tasks.md` to reflect the completion of these tasks.
This commit introduces the initial project structure for the expense tracker application. It includes the basic directory layout, configuration files, a FastAPI server with a `/process-expense` endpoint for n8n integration, and a `.gitignore` file to ensure a clean repository. This completes Phase 1 of the development plan.
