fix: agrega migración v4.6 con tablas categories y tier_discounts para tenant

pos/migrations/v4.6_inventory_support.sql

@@ -0,0 +1,20 @@
+-- Tenant DB schema v4.6 — support tables for inventory UI
+
+-- Product categories (hierarchical, optional)
+CREATE TABLE IF NOT EXISTS categories (
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(255) NOT NULL,
+    parent_id INTEGER REFERENCES categories(id) ON DELETE SET NULL,
+    is_active BOOLEAN DEFAULT true,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_categories_parent ON categories(parent_id);
+CREATE INDEX IF NOT EXISTS idx_categories_active ON categories(is_active);
+
+-- Tier-based discount configuration for price tiers 2 and 3
+CREATE TABLE IF NOT EXISTS tier_discounts (
+    tier_id INTEGER PRIMARY KEY,
+    tier_name VARCHAR(50) NOT NULL,
+    discount_pct NUMERIC(5,2) DEFAULT 0
+);