### [IMP] account_reports: Add support for selection figure type in reports

This commit adds support for selection type values in report cells that enables user to select a value from a list of available values

This values can be defined in the report XML by defining a dict as `selection={'key1': 'value1', 'key2: 'value2'}` and setting the report `figure_type` as `string`.

### [CLN] account_reports: order imports in account_report.py

### [IMP] account_reports: manage selection options in report expressions

Following the related community commit, we add the UI to allow users to edit the selection options for report expressions. We use a small hack to show the translation button for the selection options field, while still allowing users to edit the HTML/XML in the original language only. This is done to avoid users editing the HTML/XML in translations, which could break the report expressions.

We also modify the code extracting the selection options to extract them from the HTML/XML string.

### [IMP] l10n_fr_reports: add sample selection options 

THIS COMMIT SHOULD BE DELETED BEFORE MERGING. IT'S ONLY FOR TESTING PURPOSES.

**Description**
This PR implements the Belgian withholding tax reduction for extra hours/overtime (code: P.P.DEDEH) in l10n_be_hr_payroll, where it introduces support for deduction rates (66.81% and 57.75%), annual hour capping (360h standard / 450h Horeca and cash register),

**Implementation**
. Added the P.P.DEDEH salary rule linked to Belgian CP200 and applicable structures.

. A work entry type qualifies for the extra hours reduction if it is flagged as an extra hours entry (is_extra_hours = True) and satisfies the minimum surcharge requirement of at least 20%. Qualification is determined either directly on the work entry type—when its base rate is 120% or higher (amount_rate >= 1.20)—or through its associated category hierarchy. In cases where the base rate itself is lower (e.g., 100%), the system evaluates both assigned categories and optional categories for any child category marked with premium pay (is_premium_pay = True). If the combined sum of the base rate and the child category's premium percentage reaches or exceeds 120%, the work entry line successfully qualifies for the reduction.

. To calculate the reduction amount, the system first determines the employee's basic hourly wage rate by dividing their contract wage by the total worked hours in the payslip period. It then evaluates the eligible extra hours against an annual cumulative cap, set to 360 hours or 450 hours if the company uses a registered cash register, by subtracting any extra hours already claimed on prior validated or paid payslips within the same calendar year. For the remaining eligible hours, the system determines the effective rate by adding the work entry type's base rate and any applicable child category premium rates. Surcharges between 20% and 50% receive a 66.81% deduction rate, while surcharges of 50% or higher receive a 57.75% deduction rate. Finally, the total deduction is computed by multiplying the capped extra hours by the basic hourly rate and the applicable deduction percentage.

**Example**

> Scenario: An employee with a monthly wage of 2,650.00 € works 15.2 extra hours (2 days) in January 2026 under a 200% overtime rate (+100% premium $\ge 50\%$)
> . Total Monthly Worked Hours: $167.2
> . Basic Hourly Rate: 2,650.00 / 167.2 = 15.84928$
> . Extra Hours Base Amount: $15.2 *15.84928 €/h = 240.91€
> . Applicable Rate: 57.75
> . Computed Reduction Amount: $240.91 * 57.75 = -139.13€


task-5431919

## Description of the issue/feature this PR addresses:

Odoo's TCMB integration applies a single selling exchange rate everywhere,
but Turkish customers need to apply either the buying or the selling rate
depending on the transaction - a single rate doesn't fit every case. This
lets a TR company fetch both rates and explicitly select which one -
Buying or Selling - applies to a given invoice, bill, or payment.

## Current behavior before PR:

Only a single (selling) exchange rate is fetched and applied to all
invoices, bills, and payments, regardless of the direction of the
transaction.

## Desired behavior after PR is merged:

`l10n_tr_currency_live_rate` fetches and stores TCMB's buying rate
alongside the existing selling rate, and adds a Selling/Buying toggle on
invoices, bills, payments, and the Register Payment wizard. The toggle
defaults from the document's sale/purchase type or the payment's
direction, with a per-partner override that is learned from the first
document posted for that partner. Buying rates and the relabelled columns
are shown only for companies whose currency provider publishes both rates,
so nothing changes for other companies. A `pre_init_hook` backfills
existing records to the Selling rate, preserving prior behavior.

task-5017817
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