Should you build your own BlackLine?

Build a local, single-user bank reconciliation tool. No accounts, no cloud, no telemetry, no hosted anything.

Stack, non-negotiable:
- Python 3.11
- Typer for the CLI
- pandas for CSV handling
- SQLite via sqlite3 for persistence (file: recon.db)
- Jinja2 to render a static HTML report
- pytest for tests
No web server, no auth, no Docker, no external API calls.

What it does:
1. `recon import --side bank --file path.csv` and `--side ledger` ingest CSVs into SQLite. Support column mapping via a mapping.yml so the user can point date/amount/description/reference at their own headers. Store a stable row hash so re-importing the same file does not duplicate rows.
2. `recon match --period 2026-07` runs matching in passes, most confident first: (a) exact amount + exact reference, (b) exact amount within a configurable date window (default 3 days), (c) exact amount + fuzzy description via difflib ratio above a threshold, (d) many-to-one sums where several ledger lines total one bank line, capped at 4 lines to keep it tractable. Every match records the pass that made it and a confidence score.
3. `recon review --period 2026-07` interactive CLI: step through low-confidence and unmatched items, accept, reject, or tag as a known timing difference or fee. Decisions persist so re-running match does not undo human calls.
4. `recon report --period 2026-07 --out report.html` renders: opening balance, matched total, unmatched bank items, unmatched ledger items, tagged differences, and the closing difference that must reconcile to zero. Include a plain-text summary printed to stdout.
5. `recon rules` reads rules.yml for auto-tagging patterns (regex on description to category), applied during match.

Explicitly out of scope: multi-entity consolidation, FX revaluation, journal entry posting, approval workflows, ERP connectors, anything claiming to be audit evidence.

Deliverables: README with a worked example using two generated sample CSVs, mapping.yml and rules.yml examples, tests covering each matching pass plus the many-to-one case, and a Makefile with install/test/demo targets. Config paths and thresholds in .env or config.yml, never hardcoded. Print a one-line disclaimer in the report footer: this is a personal tool, not audit evidence.