Require Event Title

Steps to reproduce

1. Create new Event
2. Leave Title Field empty (or clear it)
3. Save

Expected behavior

Event creation should be blocked when no title is set.

Alternative: properly pre-set the Title as "Untitled Event"

(Left shows the CardDav when i manually enter the name as Untitled..., this shows up in Synced Calenders, Right is when I don't give any title)

Other Clients behavior:

Won't allow empty title/name:

• FossifyCalender
• Thunderbird

Allows empty Titles but prefills example Title:

• iCloud.com Calendar

Allows empty Titles:

• Nextcloud WebApp
• Gnome Calender

Actual behavior

• Event creation is not blocked.
• Nextcloud shows Event as ~"Untitled Event" (translated by me)
• Synced clients may not show the event at all (Fossify Calender with DAVx⁵)
• Nextcloud sends Email Invites: Subject 'Invitation:' 'example want's to invite you to ""' (translated by me, incl. double quotes)

Calendar app version

No response

CalDAV-clients used

• Not showing Up: DavX⁵ with Fossify Calender
• Showing: WebUI, Thunderbird, Gnome-Calender

Browser

No response

Client operating system

No response

Server operating system

No response

Web server

None

Database engine version

None

PHP engine version

None

Nextcloud version

No response

Updated from an older installed version or fresh install

None

List of activated apps

Nextcloud configuration

Web server error log

Log file

Browser log

Additional info

No response

No files, tests, or entry points are identified in the issue. Reproduce event creation with an empty title in the WebUI, then compare the behavior with the listed CalDAV clients; done means empty-title events are handled consistently and do not produce blank invitation subjects or disappear from clients.