Improve timezone handling

server/api/controller/entry.go

server/fever/fever.go

server/template/html/edit_feed.html

server/template/views.go

server/ui/controller/category.go

server/ui/controller/controller.go

server/ui/controller/entry.go

server/ui/controller/feed.go

server/ui/controller/history.go

server/ui/controller/starred.go

server/ui/controller/unread.go

storage/entry.go

storage/entry_query_builder.go

storage/feed.go