Remove brand functionality and update Bambu Lab colors

- Remove brand field from entire codebase (frontend, backend, database)
- Update Bambu Lab colors to official list with correct hex values
- Clean up unused code and type definitions
- Add database migration to drop brand column
- Update search and filters to exclude brand references
- Ensure data persistence across all application layers

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: DaX <noreply@anthropic.com>

database/migrations/004_remove_brand_column.sql

@@ -0,0 +1,2 @@
+-- Migration to remove brand column from filaments table
+ALTER TABLE filaments DROP COLUMN IF EXISTS brand CASCADE;