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>

src/components/FilamentTableV2.tsx

@@ -45,7 +45,6 @@ export const FilamentTableV2: React.FC<FilamentTableV2Props> = ({ filaments, loa
       
       return {
         id: legacy.id || `legacy-${Math.random().toString(36).substr(2, 9)}`,
-        brand: legacy.brand,
         type: legacy.tip as any || 'PLA',
         material,
         color: { name: legacy.boja, hex: legacy.bojaHex || legacy.boja_hex || '#000000' },
@@ -91,7 +90,6 @@ export const FilamentTableV2: React.FC<FilamentTableV2Props> = ({ filaments, loa
       // Search filter
       const searchLower = searchTerm.toLowerCase();
       const matchesSearch = 
-        filament.brand.toLowerCase().includes(searchLower) ||
         filament.material.base.toLowerCase().includes(searchLower) ||
         (filament.material.modifier?.toLowerCase().includes(searchLower)) ||
         filament.color.name.toLowerCase().includes(searchLower) ||
@@ -152,7 +150,7 @@ export const FilamentTableV2: React.FC<FilamentTableV2Props> = ({ filaments, loa
       <div className="relative">
         <input
           type="text"
-          placeholder="Pretraži po brendu, materijalu, boji..."
+          placeholder="Pretraži po materijalu, boji..."
           value={searchTerm}
           onChange={(e) => setSearchTerm(e.target.value)}
           className="w-full px-4 py-2 pl-10 pr-4 text-gray-700 dark:text-gray-300 bg-white dark:bg-gray-800 border border-gray-300 dark:border-gray-600 rounded-lg focus:outline-none focus:border-blue-500"