feat: build the occurrence index

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

src/types/occurrence.ts

@@ -0,0 +1,19 @@
+import type { EntityObject } from '@ChronoManager/models/entity'
+
+export interface CalendarOccurrence {
+  key: string
+  entity: EntityObject
+  occurrenceId: string | null
+  startMs: number
+  endMs: number
+  dayStartMs: number
+  durationMs: number
+  timeless: boolean
+  multiDay: boolean
+}
+
+export interface CalendarOccurrenceIndex {
+  byDay: Map<number, CalendarOccurrence[]>
+  byEntity: Map<string, CalendarOccurrence[]>
+  sorted: CalendarOccurrence[]
+}