feat: add occurrence-aware appointment search

docs/ARCHITECTURE.md

@@ -35,6 +35,11 @@ interval, count or until, weekly `BYDAY`, monthly `BYMONTHDAY`, yearly
 `BYMONTH`, and `EXDATE`. Invalid metadata retains at most the base event rather
 than crashing a render.
 
+Search matching is a pure domain predicate over normalized event text; the TUI
+owns result presentation and occurrence identity. Recurring searches expand a
+finite window of five years on either side of the selected date so an unbounded
+rule cannot turn an interactive query into unbounded work.
+
 Timed events retain their source basis: UTC, floating process-local time, or an
 IANA `TZID`. C++20 time-zone conversion keeps zoned recurrences at their civil
 wall time across daylight-saving transitions. The month grid displays instants