[FIX] web: Fix scroll issue in full calendar

Currently, When we load the Year view of the calendar then
the view is not properly scrolled top due to padding at the
top.
Calendar is scrolled to the current month but due to top
padding in year view it was not scrolled top when initially it
was loaded.

So in this commit, remove the top padding and use padding on month
so it will not have initial scroll when scroll to the particular month.

Set default calendar view to 'month'.

closes odoo/odoo#66811

Taskid: 2428655
X-original-commit: adbade3c1a000c476644e616d66af5cb982249cf
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>