Employees can now create expenses by sending an email to a configurable expense address, with automatic matching of employee, product, and amount details. The Expenses app also gets clearer onboarding, simpler expense product setup, and smoother payment handling so teams can process expense claims faster with less manual entry.

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:
## 

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1/ Modify the no content help message for hr_expense with a dynamic part
   which describe how to create a new expense by mail
2/ Mail gateway mechanism. New customizable email alias expense@domain
   that creates a new expense by sending an email to it. Check several things
- Check that the email_from is the same than one of the employees or than
   on of the related users to employees. If not, send back an email to say that
   the expense will not be created.
- If the email address is valid, check if something is between brackets '[]'
   If it is the case, check if it is linked to a product internal reference
   and set it accordingly. If nothing is found, use a default product
   'Fixed Cost'
- If one/several float(s) are found in the mail subject, take the last
   occurence and set it as the expense total amount.
  3/ If a product template is created, to not add taxes on it. We don't expect it
  to have additional taxes
  4/ Under Expenses -> Configuration -> Expense Product, use a simplified product
  view with only the needed fields.

This fix prevents an error from appearing when users choose the action to send invoices by post. It improves reliability for invoice processing and avoids an interruption in a common accounting workflow.

Description of the issue/feature this PR addresses:
- Traceback on "Send Invoices by post"

<strong>Issue: https://www.odoo.com/web#id=681170&view_type=form&model=project.issue&action=963&active_id=681&menu_id=4720</strong>

Current behavior before PR:
- Action menu Click on 'Send Invoices by post' give a traceback

Desired behavior after PR is merged:
- Solved traceback
## 

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An outdated window auto-refresh setting has been removed because it has not been supported for years. This cleanup reduces confusion for administrators and developers without changing currently supported user workflows.

This feature is no longer supported for years.

The budget management module was migrated to Odoo's newer internal framework and its files were reorganized. This should make the feature easier to maintain and test without changing the core budgeting workflow for users.

Task: https://www.odoo.com/web#id=12160&view_type=form&model=project.task&action=327&menu_id=4720

The product-related code was migrated to a newer internal framework, improving maintainability and consistency across pricing, delivery, accounting, and stock workflows. Existing pricing tests were also converted to a more reliable automated test format, helping protect business-critical product pricing behavior over time.