feat(06-02): serialize RRULE UNTIL/COUNT and lock FREQ persistence

- Add assembleRruleString() helper (exported) to outboxWorker.ts (D-06)
- Wire UNTIL/COUNT bound assembly into create + update dispatch branches
- Add recurrenceUntil (max 10) + recurrenceCount (int min 1) to outboxPayloadSchema
- Add recurrenceUntil + recurrenceCount to eventFieldsSchema in events.ts
- Series-edit bound change strips existing UNTIL/COUNT via regex before re-apply (Pitfall 3)
- All 39 broker tests pass (RED->GREEN); existing CR-01 none-wins test preserved

apps/api/src/routes/events.ts

@@ -106,6 +106,10 @@ const eventFieldsSchema = z.object({
   description: z.string().max(2000).optional(),
   recurrence: z.enum(['none', 'daily', 'weekly', 'monthly', 'yearly']).optional(),
   calendarUrl: z.string().url().max(1024).optional(),
+  // D-06: recurrence bounding (RRULE UNTIL / COUNT)
+  // T-06-02: max(10) bounds 'YYYY-MM-DD'; int().min(1) prevents zero/negative counts
+  recurrenceUntil: z.string().max(10).optional(),   // 'YYYY-MM-DD' → RRULE UNTIL
+  recurrenceCount: z.number().int().min(1).optional(), // integer ≥ 1 → RRULE COUNT
 })
 
 /** sync-status query params. */