feat: Tax settings + unified addon guide + Biteship spec

## 1. Created BITESHIP_ADDON_SPEC.md ✅
- Complete plugin specification
- Database schema, API endpoints
- WooCommerce integration
- React components
- Implementation timeline

## 2. Merged Addon Documentation ✅
Created ADDON_DEVELOPMENT_GUIDE.md (single source of truth):
- Merged ADDON_INJECTION_GUIDE.md + ADDON_HOOK_SYSTEM.md
- Two addon types: Route Injection + Hook System
- Clear examples for each type
- Best practices and troubleshooting
- Deleted old documents

## 3. Tax Settings ✅
Frontend (admin-spa/src/routes/Settings/Tax.tsx):
- Enable/disable tax calculation toggle
- Display standard/reduced/zero tax rates
- Show tax options (prices include tax, based on, display)
- Link to WooCommerce for advanced config
- Clean, simple UI

Backend (includes/Api/TaxController.php):
- GET /settings/tax - Fetch tax settings
- POST /settings/tax/toggle - Enable/disable taxes
- Fetches rates from woocommerce_tax_rates table
- Clears WooCommerce cache on update

## 4. Advanced Local Pickup - TODO
Will be simple: Admin adds multiple pickup locations

## Key Decisions:
✅ Hook system = No hardcoding, zero coupling
✅ Tax settings = Simple toggle + view, advanced in WC
✅ Single addon guide = One source of truth

Next: Advanced Local Pickup locations

includes/Api/TaxController.php

@@ -0,0 +1,156 @@
+<?php
+/**
+ * Tax Settings REST API Controller
+ *
+ * @package WooNooW
+ */
+
+namespace WooNooW\Api;
+
+use WP_REST_Controller;
+use WP_REST_Server;
+use WP_REST_Request;
+use WP_REST_Response;
+use WP_Error;
+
+class TaxController extends WP_REST_Controller {
+
+	/**
+	 * Register routes
+	 */
+	public function register_routes() {
+		$namespace = 'woonoow/v1';
+
+		// Get tax settings
+		register_rest_route(
+			$namespace,
+			'/settings/tax',
+			array(
+				'methods'             => WP_REST_Server::READABLE,
+				'callback'            => array( $this, 'get_settings' ),
+				'permission_callback' => array( $this, 'check_permission' ),
+			)
+		);
+
+		// Toggle tax calculation
+		register_rest_route(
+			$namespace,
+			'/settings/tax/toggle',
+			array(
+				'methods'             => WP_REST_Server::CREATABLE,
+				'callback'            => array( $this, 'toggle_tax' ),
+				'permission_callback' => array( $this, 'check_permission' ),
+				'args'                => array(
+					'enabled' => array(
+						'required'          => true,
+						'type'              => 'boolean',
+						'sanitize_callback' => 'rest_sanitize_boolean',
+					),
+				),
+			)
+		);
+	}
+
+	/**
+	 * Check permission
+	 */
+	public function check_permission() {
+		return current_user_can( 'manage_woocommerce' );
+	}
+
+	/**
+	 * Get tax settings
+	 */
+	public function get_settings( WP_REST_Request $request ) {
+		try {
+			$settings = array(
+				'calc_taxes'          => get_option( 'woocommerce_calc_taxes', 'no' ),
+				'prices_include_tax'  => get_option( 'woocommerce_prices_include_tax', 'no' ),
+				'tax_based_on'        => get_option( 'woocommerce_tax_based_on', 'shipping' ),
+				'tax_display_shop'    => get_option( 'woocommerce_tax_display_shop', 'excl' ),
+				'tax_display_cart'    => get_option( 'woocommerce_tax_display_cart', 'excl' ),
+				'standard_rates'      => $this->get_tax_rates( 'standard' ),
+				'reduced_rates'       => $this->get_tax_rates( 'reduced-rate' ),
+				'zero_rates'          => $this->get_tax_rates( 'zero-rate' ),
+			);
+
+			return new WP_REST_Response( $settings, 200 );
+		} catch ( \Exception $e ) {
+			return new WP_REST_Response(
+				array(
+					'error'   => 'fetch_failed',
+					'message' => $e->getMessage(),
+				),
+				500
+			);
+		}
+	}
+
+	/**
+	 * Toggle tax calculation
+	 */
+	public function toggle_tax( WP_REST_Request $request ) {
+		try {
+			$enabled = $request->get_param( 'enabled' );
+			$value   = $enabled ? 'yes' : 'no';
+
+			update_option( 'woocommerce_calc_taxes', $value );
+
+			// Clear WooCommerce cache
+			\WC_Cache_Helper::invalidate_cache_group( 'taxes' );
+			\WC_Cache_Helper::get_transient_version( 'shipping', true );
+
+			return new WP_REST_Response(
+				array(
+					'success' => true,
+					'enabled' => $enabled,
+					'message' => $enabled 
+						? __( 'Tax calculation enabled', 'woonoow' )
+						: __( 'Tax calculation disabled', 'woonoow' ),
+				),
+				200
+			);
+		} catch ( \Exception $e ) {
+			return new WP_REST_Response(
+				array(
+					'error'   => 'update_failed',
+					'message' => $e->getMessage(),
+				),
+				500
+			);
+		}
+	}
+
+	/**
+	 * Get tax rates for a specific class
+	 */
+	private function get_tax_rates( $tax_class ) {
+		global $wpdb;
+
+		$rates = $wpdb->get_results(
+			$wpdb->prepare(
+				"SELECT * FROM {$wpdb->prefix}woocommerce_tax_rates 
+				WHERE tax_rate_class = %s 
+				ORDER BY tax_rate_order ASC",
+				$tax_class
+			)
+		);
+
+		$formatted_rates = array();
+
+		foreach ( $rates as $rate ) {
+			$formatted_rates[] = array(
+				'id'       => $rate->tax_rate_id,
+				'country'  => $rate->tax_rate_country,
+				'state'    => $rate->tax_rate_state,
+				'rate'     => $rate->tax_rate,
+				'name'     => $rate->tax_rate_name,
+				'priority' => $rate->tax_rate_priority,
+				'compound' => $rate->tax_rate_compound,
+				'shipping' => $rate->tax_rate_shipping,
+			);
+		}
+
+		return $formatted_rates;
+	}
+}