Added brand/ directory to custom_components/tibber_prices/ with all
8 supported PNG variants, generated from existing SVGs in images/:
- icon.png / dark_icon.png (256×256)
- icon@2x.png / dark_icon@2x.png (512×512)
- logo.png / dark_logo.png (500×128)
- logo@2x.png / dark_logo@2x.png (1000×256)
Local brand images automatically take priority over CDN images and
are served via the HA brands proxy API (/api/brands/integration/).
Silently ignored on HA < 2026.3, no changes to manifest.json needed.
Updated AGENTS.md to document the brand/ directory under "ALLOWED in root".
Impact: Integration icon and logo now display correctly in HA ≥ 2026.3
without requiring a separate submission to the HA brands repository.
