US-4.6implemented Detect uncategorised transactions before interactive matching
As a user running `./start.sh` I want uncategorised bank CSV transactions to be detected and reported immediately — before the interactive matching step — via a dedicated `--check-categorisation` flag so that I don't waste time on manual receipt-to-CSV or CSV-to-CSV matching only to discover a categorisation error afterwards.
Acceptance Criteria
- `start.sh` calls `hledger_preprocessor --check-categorisation` right after config validation, before `--match-transactions`.
- The check loads all bank CSV transactions and runs the rule-based classifier on each one (dry-run — no file output).
- If any transaction raises `UncategorisedTransactionError`, the check collects ALL such errors and prints them as a single summary, then exits non-zero.
- Receipt-based `AccountTransaction`s are NOT checked (their category comes from the TUI label and is always present).
- The check is fast: it only loads CSVs and runs classification — no file I/O or directory creation.
No DAG diagram: Pre-flight validation step — the data path mirrors US-C.1 but without any output; it is a guard gate that runs before US-4.1.
Demo video coming soon