Add scheduled dispatch support (edit + authoritative view)

Editing (game port, OpenTTDClient): a core of JGRPP's scheduled dispatch
DoCommands — set_scheduled_dispatch (enable/disable), add/remove schedule,
add/remove/clear slots, and set duration/start date. Adds the command IDs
to protocol.py.

Viewing (admin, OpenTTDAdminClient.get_dispatch): the GameScript API has no
dispatch support, so a new server patch (docker/patches/0002-*) adds
read-only GSOrder.GetScheduledDispatch* / IsScheduledDispatchEnabled
getters, an AdminBridge GameScript get_dispatch handler exposes them, and
get_dispatch() returns the live schedules and slots (mirrors get_timetable).

Note: set_dispatch_start_date values are normalised by the engine relative
to current game time, so they read back offset from the requested value.

Includes unit + e2e tests, a demo in main.py, and protocol/timetable docs.
The AdminBridge GameScript and the patched OpenTTD-patches clone live
outside this repo; the 0002 patch file is the durable source for the latter.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docker/patches/README.md

@@ -15,6 +15,14 @@ Current patches:
   GameScript's `get_timetable` command and the Python client's
   `OpenTTDAdminClient.get_timetable()`.
 
+- `0002-Add-GameScript-API-scheduled-dispatch-getters-to-Scr.patch` — adds read-only scheduled
+  dispatch getters (`GetScheduledDispatchScheduleCount`, `IsScheduledDispatchEnabled`,
+  `GetScheduledDispatchDuration`, `GetScheduledDispatchStartTick`, `GetScheduledDispatchDelay`,
+  `GetScheduledDispatchReuseSlots`, `GetScheduledDispatchSlotCount`,
+  `GetScheduledDispatchSlotOffset`, `GetScheduledDispatchSlotFlags`) to the `GSOrder` GameScript
+  class. Required by the AdminBridge GameScript's `get_dispatch` command and the Python client's
+  `OpenTTDAdminClient.get_dispatch()`.
+
 ## Applying after a fresh clone
 
 ```bash