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>

api/migrate.js

@@ -61,10 +61,9 @@ async function migrate() {
         // Import filaments
         for (const item of legacyData) {
           await pool.query(
-            `INSERT INTO filaments (brand, tip, finish, boja, boja_hex, refill, vakum, otvoreno, kolicina, cena) 
-             VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)`,
+            `INSERT INTO filaments (tip, finish, boja, boja_hex, refill, vakum, otvoreno, kolicina, cena) 
+             VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)`,
             [
-              item.brand,
               item.tip,
               item.finish,
               item.boja,