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.
Updates the tasks.md file to a checklist format to track progress.
- Marks Phase 1 setup tasks as complete.
- Adds a note clarifying that n8n will be used for webhook handling instead of a direct Telegram integration in the app.