Ask shared accounts together, and about files only when Files opens

At sign-in the files, contacts and calendar stores each asked every shared
account a question, one account after another: a request apiece before the
reader had opened any of those views.

Files now only works out at sign-in whether it is available. Which shared
accounts hold files is asked when the Files view or the file picker opens,
which the Files view already did on every visit. Shared address books and
calendars are asked for in one request, and the calendar store loads its
calendars, identities and shared calendars side by side.

web/src/store/contacts.ts

@@ -294,7 +294,9 @@ export const useContacts = create<ContactsState>((set, get) => ({
     }
     const books: SharedBook[] = [];
     const cards: Record<string, ContactCard> = {};
-    for (const [accountId, account] of accounts) {
+    // Every account at once: calls made in one tick share a request, where a
+    // loop sent one after another for each account shared with the reader.
+    await Promise.all(accounts.map(async ([accountId, account]) => {
       try {
         const res = await client.call<GetResponse<AddressBook>>("AddressBook/get", { accountId, ids: null, properties: ADDRESS_BOOK_PROPS });
         for (const book of res.list) books.push({ accountId, accountName: account.name, book });
@@ -310,7 +312,7 @@ export const useContacts = create<ContactsState>((set, get) => ({
          */
         const added = new Set(useSettings.getState().settings.addedShares);
         const wanted = new Set(res.list.filter((b) => b.isSubscribed || added.has(sharedKey(accountId, b.id))).map((b) => b.id));
-        if (!wanted.size) continue;
+        if (!wanted.size) return;
         // One page. A shared book is a colleague's contacts, not an archive,
         // and the alternative is holding the reader's own list hostage to it.
         const cardsRes = await client.chain([
@@ -325,9 +327,11 @@ export const useContacts = create<ContactsState>((set, get) => ({
       } catch {
         // An account that refuses is one that shared nothing here. Not an
         // error to show: the reader did not ask for it and cannot act on it.
-        continue;
       }
-    }
+    }));
+    // Answers arrive in any order; list the books in the session's.
+    const order = new Map(accounts.map(([id], i) => [id, i]));
+    books.sort((a, b) => (order.get(a.accountId) ?? 0) - (order.get(b.accountId) ?? 0));
     set({ sharedBooks: books, sharedCards: cards, sharedLoaded: true });
   },