Fix: Replace deprecated double(11,2) with decimal(10,2) in ext_tables.sql

[kitzberger]

The ext_tables.sql file used the deprecated MySQL syntax double(11,2) for decimal fields, which causes constant schema migration prompts when running DB compare.

MySQL/MariaDB interprets double(11,2) ambiguously, and Doctrine DBAL schema comparison detected a type mismatch between the defined schema and what TYPO3 generates from TCA configuration. The TCA defines these fields as type => 'number' with format => 'decimal', which TYPO3's DefaultTcaSchema class converts to decimal(10,2).

This change replaces all occurrences of double(11,2) with decimal(10,2) to align with TYPO3's schema generation and eliminate the persistent migration warnings.

Affected fields:

• tx_cart_domain_model_order_item: gross, net, total_gross, total_net
• tx_cart_domain_model_order_taxclass: calc
• tx_cart_domain_model_order_tax: tax
• tx_cart_domain_model_order_product: price, discount, gross, net, tax
• tx_cart_domain_model_order_discount: gross, net, tax
• tx_cart_domain_model_order_shipping: gross, net, tax
• tx_cart_domain_model_order_payment: gross, net, tax
• tx_cart_domain_model_coupon: discount, cart_min_price

Resolves: #711