gitweb: let page header grow on mobile for long wrapped project names

gitweb: let page header grow on mobile for long wrapped project names

On mobile, long project names in the page header can wrap to multiple lines,
but the fixed 25px header height does not grow with wrapped content.

Switch the header from fixed height to min-height so it expands as needed
while keeping the same baseline height for single-line titles.

Signed-off-by: Rito Rhymes <rito@ritovision.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>