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/utils/eventFormatters.ts

@@ -5,7 +5,7 @@ import {
   DAY_TO_GERMAN_SHORT,
   MONTH_TO_GERMAN,
   ExpandedEvent,
-} from "@caldav/shared";
+} from "@calchat/shared";
 import { EventRepository } from "../services/interfaces";
 import { expandRecurringEvents } from "./recurrenceExpander";
 

apps/server/src/utils/recurrenceExpander.ts

@@ -1,5 +1,5 @@
 import { RRule, rrulestr } from "rrule";
-import { CalendarEvent, ExpandedEvent } from "@caldav/shared";
+import { CalendarEvent, ExpandedEvent } from "@calchat/shared";
 
 // Convert local time to "fake UTC" for rrule
 // rrule interprets all dates as UTC internally, so we need to trick it