Allow duplicating events from subscribed calendars into my own calendars

User Story
As a Proton Calendar user with subscribed calendars (ICS subscriptions, e.g. sports club, league or holiday calendars), I want to duplicate a single event from a subscribed calendar into one of my own calendars, so that I don't have to re-create it manually field by field.

Current situation / Problem
For my own events, the event popup offers a "Duplicate event" action.
For events from subscribed calendars, this action is missing entirely - subscribed calendars are read-only, which is correct for the calendar itself.
But when I want to permanently take over a single event from a subscribed calendar into my personal calendar (to adjust it, set reminders, or invite participants), I currently have to retype title, date, time, location and description by hand.
That is unnecessary manual work for a capability that already exists for my own events.

Desired behaviour (acceptance criteria)
The user can duplicate an event from a subscribed calendar.
When duplicating, the user can choose the target calendar from their own (writable) calendars.
The duplicate carries over the original event's title, date and time, location and description.
The user can then edit the duplicate like any of their own events (reminders, participants, times, deletion).
The original event in the subscribed calendar remains unchanged.

Out of scope
Making subscribed calendars editable - they should stay read-only.
Any sync or link between the duplicate and the original event - the duplicate is an independent copy.

Value
Consistency: the duplicate action already exists for own events - users expect it for subscribed events too.
Saves manual re-entry work and avoids typos.
Likely low implementation effort, since the duplicate function and the event editor already exist; what's essentially missing is the entry point in the popup of subscribed-calendar events.