Base module for Bank Statement Import

This module does not add a menu or a button on its own; it prepares the ground so that bank statement import modules (from files or from online bank feeds) can work safely and quickly.

What it changes for users: - Each imported bank statement line gets an "Import ID" that identifies the original transaction coming from the bank. Odoo enforces that this identifier is unique, so the same bank transaction cannot be imported twice. If someone tries, Odoo blocks it with the message "A bank account transaction can be imported only once!". - The original data received from the bank is stored on the statement line and shown in a read-only "Raw Data" section on the bank statement line form, so users can always check what the bank actually sent.

Automatic behaviours added: - Bank account numbers coming from the import are cleaned up (sanitized) before being used. - When a statement line has a bank account number, Odoo automatically looks for a matching bank account already registered on a partner and fills in the partner and bank account on the line. - The import identifier is built from the sanitized account number, the journal and the bank's own transaction reference, which makes duplicates detectable across imports.

It touches the bank statement line (account.bank.statement.line) and the journal (account.journal) models, and extends the bank statement line form view.