fix(topbar): render filament icons in the bundled Momcake face

[gmmcosta15]

Description

• Bug fix

• Add lib/utils/fonts.py with a cached register_momcake().

• Bundle the Momcake Thin and Bold faces in the qrc.

• Correct the topbar .svg assets to name Momcake Pro, the family Qt files them under.

• Call register_momcake() from updatePage before first paint.

Motivation

Nothing registered the family the topbar .svg files declare, so all of them rendered in the system fallback.

Tests

make check green; the PR 2 font test asserts no substitution.