## Issue
When exporting the General Ledger in xlsx format with only one journal selected, the tax declaration lines appear multiple times and are disrupt the overall format of the report.

## Steps to reproduce
1. Install *Accounting* (`account_accountant`) with demo data
2. In Accounting > Reporting > General Ledger, select a single journal (e.g. Customer Invoices) and click the *XLSX* export button.
3. **The resulting XLSX file is incorreclty formated. The tax declaration lines appear multiple times and disrupt the structure of the report.**

<img width="1012" height="603" alt="image" src="https://github.com/user-attachments/assets/1d22e9a1-3fc2-4538-b1bd-4ca1d1bbe092" />


## Cause
Since https://github.com/odoo/enterprise/commit/6a3804c5fe6b4f1d48a4ab311a0f1fbb24d75187, the xlsx report is generated by iterating over the relevant accounts and injecting the lines into the report account by account.

https://github.com/odoo/enterprise/blob/b6d27f428e2b966e38b65e820e1454b711483996/account_reports/models/account_general_ledger.py#L773-L775

The [`_get_accounts_with_move_lines` method](https://github.com/odoo/enterprise/blob/17.0/account_reports/models/account_general_ledger.py#L814) does not take into account the journals that are requested when exporting .xlxs, which leads to too many accounts being iterated over.

Before that commit, the `_get_lines` method was only called once when generating the xlsx report. This explains the behaviors below, that were not properly adapted to call the method multiple times to generate a single report.

The first issue is that the `_get_lines` method calls the `_dynamic_lines_generator` method, which adds the tax declaration lines after each account when only one journal is selected:

https://github.com/odoo/enterprise/blob/b6d27f428e2b966e38b65e820e1454b711483996/account_reports/models/account_general_ledger.py#L88-L91

To avoid that, we can add a context key to prevent the injection of the tax declaration lines for all iterations, then add the lines afterwards.

Another issue is that the accounts chosen to iterate over do not take the selected journal into account. Without doing so, we iterate over too many accounts, which is inefficient, but which also adds the tax declaration lines (and only those lines) for those irrelevant accounts. That is why the tax declaration lines appear multiple times in the incorrect reports: they were added for accounts that were not supposed to belong in the report.

Lastly, because the total line is added individually, it would not be bold because of the following condition from `inject_lines_into_xlsx_sheeŧ`:

https://github.com/odoo/enterprise/blob/b6d27f428e2b966e38b65e820e1454b711483996/account_reports/models/account_report.py#L5262-L5266

## Performance Impact
Because the commit introducing the issue (https://github.com/odoo/enterprise/commit/6a3804c5fe6b4f1d48a4ab311a0f1fbb24d75187) is a [PERF] commit, the performance impact of this fix was evaluated. The table below shows the time taken to export the XLSX report of the General Ledger for a various amounts of `account.move.line`. Each value represents the average execution time over 10 runs (in milliseconds), with the standard deviation shown in parentheses.

|        | Before (ms)      | After (ms)       |
|--------|------------------|------------------|
| 100    | 321.25 (± 49.56) | 363.43 (± 59.93) |
| 5,000  | 1759 (± 71.87)   | 1773 (± 60.19)   |
| 10,000 | 2723 (± 70.72)   | 2765 (± 106.8)   |
| 50,000 | 11501 (± 170.32) | 11567 (± 165.87) |


opw-5783588