fix(activity): revert to synthetic schedule - real ids black-screen the events page

The events page NREs when the schedule references real activities: the
client renders their panels and requests per-activity data
(GetActivityHotData/GetActiveActivityData/...) that this PS cannot fill
yet, Sync(nil) -> black screen. The synthetic list resolves to nothing
and keeps the page open (empty but usable).

realActivitySchedule stays in handlers_activity_data.go for the future
round where per-activity data handlers exist.

persistent

@@ -1,20 +1,20 @@
 {
   "lineups": {
-    "0": 1001,
-    "1": 1002,
-    "2": 1003,
-    "3": 1004
+    "0": 1506,
+    "1": 1501,
+    "2": 1502,
+    "3": 1503
   },
   "position": {
-    "x": -92,
-    "y": 4278,
-    "z": 68083,
-    "rot_y": 155566
+    "x": -13238,
+    "y": 592,
+    "z": 86502,
+    "rot_y": 290000
   },
   "scene": {
-    "plane_id": 10202,
-    "floor_id": 10202001,
-    "entry_id": 102020107
+    "plane_id": 20331,
+    "floor_id": 20331001,
+    "entry_id": 2033101
   },
   "main_character": "FemaleHarmony",
   "march_type": "MarchHunt",