refactor: consolidate and debloat calendar sync implementation

Merge duplicated Google/Outlook engines, background handlers, and API
layers into shared calendarSync modules to cut complexity without changing
user-facing sync behavior.

src/seqta/utils/outlookCalendar/storage.ts

@@ -1,38 +1,8 @@
-import browser from "webextension-polyfill";
-import type { GoogleCalendarEventMapEntry } from "@/seqta/utils/googleCalendar/eventMapEntry";
-
-export const BSPLUS_OUTLOOK_CALENDAR_STORAGE_KEY = "bsplus_outlook_calendar";
-
-export interface OutlookCalendarStoredState {
-  accessToken?: string;
-  refreshToken?: string;
-  expiresAt?: number;
-  connectedAt?: number;
-  lastSyncAt?: number;
-  lastSyncOrigin?: string;
-  eventMap?: Record<string, string | GoogleCalendarEventMapEntry>;
-}
-
-export async function readOutlookCalendarState(): Promise<OutlookCalendarStoredState> {
-  const got = await browser.storage.local.get(BSPLUS_OUTLOOK_CALENDAR_STORAGE_KEY);
-  const raw = got[BSPLUS_OUTLOOK_CALENDAR_STORAGE_KEY];
-  if (!raw || typeof raw !== "object" || Array.isArray(raw)) return {};
-  return raw as OutlookCalendarStoredState;
-}
-
-export async function writeOutlookCalendarState(
-  patch: Partial<OutlookCalendarStoredState>,
-): Promise<OutlookCalendarStoredState> {
-  const current = await readOutlookCalendarState();
-  const next: OutlookCalendarStoredState = { ...current, ...patch };
-  await browser.storage.local.set({ [BSPLUS_OUTLOOK_CALENDAR_STORAGE_KEY]: next });
-  return next;
-}
-
-export async function clearOutlookCalendarState(): Promise<void> {
-  await browser.storage.local.remove(BSPLUS_OUTLOOK_CALENDAR_STORAGE_KEY);
-}
-
-export function outlookEventMapKey(origin: string, seqtaKey: string): string {
-  return `${origin}::${seqtaKey}`;
-}
+export {
+  BSPLUS_OUTLOOK_CALENDAR_STORAGE_KEY,
+  clearOutlookCalendarState,
+  readOutlookCalendarState,
+  writeOutlookCalendarState,
+  type OutlookCalendarStatus,
+  type OutlookCalendarStoredState,
+} from "@/seqta/utils/calendarSync/providerStorage";