fix(app): Backport "duplicate postcss plugins" fix from Qv2
fix(app): Backport "duplicate postcss plugins" fix from Qv2

rstoenescu/quasar-framework,pdanpdan/quasar,quasarframework/quasar,quasarframework/quasar,pdanpdan/quasar,rstoenescu/quasar-framework,rstoenescu/quasar-framework,quasarframework/quasar,pdanpdan/quasar,quasarframework/quasar,pdanpdan/quasar