refactor: rename package scope from @caldav to @calchat

Rename all workspace packages to reflect the actual project name:
- @caldav/client -> @calchat/client
- @caldav/server -> @calchat/server
- @caldav/shared -> @calchat/shared
- Root package: caldav-mono -> calchat-mono

Update all import statements across client and server to use the new
package names. Update default MongoDB database name and logging service
identifier accordingly.

apps/server/src/repositories/mongo/models/UserModel.ts

@@ -1,5 +1,5 @@
 import mongoose, { Schema, Document, Model } from "mongoose";
-import { User } from "@caldav/shared";
+import { User } from "@calchat/shared";
 import { IdVirtual } from "./types";
 
 export interface UserDocument extends Omit<User, "id">, Document {