Use display name instead of username for shared calendar owners

Add db.DisplayName(username), returning the user's display name if
set, otherwise the raw username. Use it everywhere a shared calendar's
owner is shown: the web calendar legend ("shared by ..."), the "new
event"/edit calendar select label, the dashboard's "Shared with you"
list, and the CalDAV-side description/name-collision disambiguation
("Name (Owner)") shown to CalDAV clients like DAVx5.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

internal/web/calendar.go

@@ -444,7 +444,7 @@ func (s *Server) collectCalendarEvents(username string, gridStart, gridEnd time.
 			hasWritable = true
 		}
 		calSummaries = append(calSummaries, templates.CalendarSummary{
-			Ref: entry.Ref, Name: entry.Name, Owner: entry.Owner, Color: entry.Color,
+			Ref: entry.Ref, Name: entry.Name, Owner: s.dbase.DisplayName(entry.Owner), Color: entry.Color,
 			Shared: entry.Owner != username, Writable: entry.Writable, Virtual: entry.Virtual,
 		})
 
@@ -565,7 +565,7 @@ func (s *Server) handleEventNew(w http.ResponseWriter, r *http.Request) {
 		}
 		label := e.Name
 		if e.Owner != username {
-			label = e.Name + " (" + e.Owner + ")"
+			label = e.Name + " (" + s.dbase.DisplayName(e.Owner) + ")"
 		}
 		options = append(options, templates.CalendarOption{Ref: e.Ref, Label: label})
 	}
@@ -668,7 +668,7 @@ func (s *Server) handleEventEdit(w http.ResponseWriter, r *http.Request) {
 		form.CalRef = ref
 		label := name
 		if owner != username {
-			label = name + " (" + owner + ")"
+			label = name + " (" + s.dbase.DisplayName(owner) + ")"
 		}
 		form.CalendarLabel = label
 		form.Writable = owner == username

internal/web/dashboard.go

@@ -26,7 +26,7 @@ func (s *Server) handleDashboard(w http.ResponseWriter, r *http.Request) {
 	}
 	for _, sh := range calShares {
 		sharedWithMe = append(sharedWithMe, templates.SharedWithMeItem{
-			Kind: "calendar", Owner: sh.Owner, Name: sh.CalendarName, Permission: string(sh.Permission),
+			Kind: "calendar", Owner: s.dbase.DisplayName(sh.Owner), Name: sh.CalendarName, Permission: string(sh.Permission),
 		})
 	}
 	bookShares, err := s.dbase.AddressBooksSharedWith(username)
@@ -35,7 +35,7 @@ func (s *Server) handleDashboard(w http.ResponseWriter, r *http.Request) {
 	}
 	for _, sh := range bookShares {
 		sharedWithMe = append(sharedWithMe, templates.SharedWithMeItem{
-			Kind: "addressbook", Owner: sh.Owner, Name: sh.AddressBookName, Permission: string(sh.Permission),
+			Kind: "addressbook", Owner: s.dbase.DisplayName(sh.Owner), Name: sh.AddressBookName, Permission: string(sh.Permission),
 		})
 	}