brand: use official Victron icons from home-assistant/brands

Replace AI-generated icons with the existing official Victron artwork
from home-assistant/brands/custom_integrations/victron_mqtt.

Since HA 2026.3 the Brands Proxy API serves icons from the integration's
local brand/ folder first, falling back to the central brands CDN.
Shipping the icons locally fixes the empty-placeholder view in the HA
integration list without changing the visual branding.

Author: pos-ei-don