Auto-categorize with built-in merchant rules, payee category editor, income/net on dashboard

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

README.md

@@ -21,6 +21,10 @@ AppID=money PUID=1000 PGID=1000 TZ=America/New_York docker compose up -d   # the
 "Create a blank workbook" button that copies it into the data folder. Then drop statements in; new payees land on the Lists tab as
 "Other / Unsorted" for you to categorize. `loader_rules.example.json` shows the private rules file format.
 
+## Categories
+New payees are categorized by built-in generic merchant rules (`seed_rules.py`); anything unknown lands in "Other / Unsorted".
+Use the **Categorize payees** card in the app (or the Lists tab) to set the rest. Your choices are saved in the workbook.
+
 ## Personal rules (not in git)
 Your name, card last-4 and similar live in `loader_rules.json` next to the workbook (git-ignored, not in the image):
 ```json