Refactor to multi-category catalog with polished light mode

- Restructure from single filament table to multi-category product catalog
  (filamenti, stampaci, ploce, mlaznice, delovi, oprema)
- Add shared layout components (SiteHeader, SiteFooter, CategoryNav, Breadcrumb)
- Add reusable UI primitives (Badge, Button, Card, Modal, PriceDisplay, EmptyState)
- Add catalog components (CatalogPage, ProductTable, ProductGrid, FilamentCard, ProductCard)
- Add admin dashboard with sidebar navigation and category management
- Add product API endpoints and database migrations
- Add SEO pages (politika-privatnosti, uslovi-koriscenja, robots.txt, sitemap.xml)
- Fix light mode: gradient text contrast, category nav accessibility,
  surface tokens, card shadows, CTA section theming

database/migrations/021_create_products_table.sql

@@ -0,0 +1,32 @@
+-- Migration: Create products table for non-filament product categories
+-- This is purely additive - does not modify existing tables
+
+CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
+
+CREATE TYPE product_category AS ENUM ('printer', 'build_plate', 'nozzle', 'spare_part', 'accessory');
+CREATE TYPE product_condition AS ENUM ('new', 'used_like_new', 'used_good', 'used_fair');
+
+CREATE TABLE products (
+  id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+  category product_category NOT NULL,
+  name VARCHAR(255) NOT NULL,
+  slug VARCHAR(255) NOT NULL UNIQUE,
+  description TEXT,
+  price INTEGER,
+  condition product_condition DEFAULT 'new',
+  stock INTEGER NOT NULL DEFAULT 0 CHECK (stock >= 0),
+  sale_percentage INTEGER DEFAULT 0,
+  sale_active BOOLEAN DEFAULT FALSE,
+  sale_start_date TIMESTAMP WITH TIME ZONE,
+  sale_end_date TIMESTAMP WITH TIME ZONE,
+  attributes JSONB NOT NULL DEFAULT '{}',
+  image_url VARCHAR(500),
+  is_active BOOLEAN DEFAULT TRUE,
+  created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+  updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE INDEX idx_products_category ON products(category);
+CREATE INDEX idx_products_slug ON products(slug);
+CREATE INDEX idx_products_is_active ON products(is_active);
+CREATE INDEX idx_products_category_active ON products(category, is_active);

database/migrations/022_create_printer_compatibility.sql

@@ -0,0 +1,25 @@
+-- Migration: Create printer models and product compatibility junction table
+
+CREATE TABLE printer_models (
+  id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+  name VARCHAR(100) NOT NULL UNIQUE,
+  series VARCHAR(50) NOT NULL
+);
+
+CREATE TABLE product_printer_compatibility (
+  product_id UUID REFERENCES products(id) ON DELETE CASCADE,
+  printer_model_id UUID REFERENCES printer_models(id) ON DELETE CASCADE,
+  PRIMARY KEY (product_id, printer_model_id)
+);
+
+-- Seed printer models
+INSERT INTO printer_models (name, series) VALUES
+  ('A1 Mini', 'A'),
+  ('A1', 'A'),
+  ('P1P', 'P'),
+  ('P1S', 'P'),
+  ('X1C', 'X'),
+  ('X1E', 'X'),
+  ('H2D', 'H'),
+  ('H2S', 'H'),
+  ('P2S', 'P');

database/migrations/023_create_product_images.sql

@@ -0,0 +1,12 @@
+-- Migration: Multi-image support for products
+
+CREATE TABLE product_images (
+  id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+  product_id UUID NOT NULL REFERENCES products(id) ON DELETE CASCADE,
+  url VARCHAR(500) NOT NULL,
+  alt_text VARCHAR(255),
+  sort_order INTEGER DEFAULT 0,
+  created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE INDEX idx_product_images_product_id ON product_images(product_id);