feat: add "olderThan" segment filter operator

- Added `olderThan` and `triggeredOlderThan` operators to types and schemas
- Implemented backend logic for `olderThan` operator in SegmentService
- Updated SegmentFilterBuilder and shared index/types files to support new time-based operators

packages/shared/src/schemas/index.ts

@@ -101,8 +101,10 @@ const segmentFilterSchema = z.object({
     'exists',
     'notExists',
     'within',
+    'olderThan',
     'triggered',
     'triggeredWithin',
+    'triggeredOlderThan',
     'notTriggered',
   ]),
   value: z.any().optional(),