feat: replace Цена column with Крайняя цена and Цена закрытия in Excel output

docs: add multi-security-type spec and implementation plan

fix: add exchange_ppif type mapping, fallback close_price from PREVLEGALCLOSEPRICE

fix: find type column by name in resolve_isin (was hardcoded to index 1)

chore: final formatting and AGENTS.md update

add visitor pattern

add template method pattern

add strategy pattern

add state pattern

add observer pattern

add memento pattern

add mediator pattern

add iterator pattern

add command pattern

add chain of responsibility pattern

add proxy pattern

add flyweight pattern

add facade pattern

add decorator pattern

add composite pattern

add bridge pattern

add adapter pattern