When opening reports with `default_opening_date_filter='this_year'`(e.g., P&L, Partner Ledger), the date filter dropdown showed incorrect defaults for non-selected period types:
- Month showed the last month of the fiscal year (e.g., December)
  instead of the current month
- Quarter showed Q4 instead of the current quarter

This happened because `initDateFilterState()` used the backend's `date_to` (fiscal year end) as the reference for computing all filter periods. For `this_year`, `date_to` is the year-end date (e.g., 2026-12-31), so `computePeriodRange()` for month/quarter returned periods containing that date rather than today's date. Reports with `this_month` or `today` defaults were unaffected because their `date_to` is naturally close to today.

Now, non-selected filters use today as their reference date on initial load whenever today falls within the report period, while the selected filter continues to use the backend's `date_to`, preserving the alignment behavior introduced in the date filter refactor (https://github.com/odoo/enterprise/commit/40484f985f511edd7ba2ae759ce63ef564bcf1f7).

Additionally, selecting the custom comparison filter now triggers an immediate reload so its default date range is recomputed by the backend. The custom comparison range is initialized using the current fiscal year up to today, capping its end date to today instead of inheriting the report's `date_to`, which could otherwise default to a future date for yearly reports.

task-6229588

Forward-Port-Of: odoo/enterprise#127292
Forward-Port-Of: odoo/enterprise#121638