feat: implement simple weekly recurrence rendering

- Add `simple_weekly` type and `weekly` field to `rem` record
- Add `exdate` field to `rem` for excluded dates
- Add `collect_exdates` collector to pipeline
- implement weekly `RRULE` handling with `BYDAY`, `INTERVAL`,
  `COUNT`/`UNTIL`
- Add `render_weekly` to emit one `REM` per weekday with `UNTIL`/`*N`
- Replace `timedesc_of_date_or_datetime` with
  `timedesc_of_utc_or_timestamp_local` in utils
- Refactor `get_exdates`/`get_rdates` to separate dates, datetimes and
  periods; add debug logging per UID
- Wrap reminder output in try/catch in main; drop trailing newline
  duplication
- Mark implemented predicates (P00–P05, P09, P12, P14) with ✅;
  remove P18–P20 (ignored/deferred)

bin/main.ml

@@ -58,6 +58,9 @@ let ical2rem ical_files =
           good_rems_acc)
   in
 
-  ListLabels.iter good_rems ~f:(fun rem -> Printf.printf "%s\n" (Remind.string_of_rem rem))
+  try ListLabels.iter good_rems ~f:(fun rem -> Printf.printf "%s" (Remind.string_of_rem rem))
+  with e ->
+    Printf.eprintf "Error processing reminders: %s\n" (Printexc.to_string e);
+    exit 1
 
 let () = if !Sys.interactive then () else exit (CommandLine.main ical2rem)