Use region-prioritized release dates from ScreenScraper and IGDB

[Copilot]

Scanner metadata was already region-aware for some fields, but first_release_date still resolved to a generic/global value. This caused multi-region ROMs to receive the same release date even when provider data exposed region-specific dates.

• ScreenScraper (SS.fr): region-aware date selection

  • Updated SS metadata extraction to resolve first_release_date using the same region priority flow as other regional fields (rom.regions + SCAN_REGION_PRIORITY fallbacks).
  • Date parsing behavior is unchanged (YYYY-MM-DD, then YYYY fallback), but selection is now performed per preferred region before global fallback.

• IGDB: release_dates-based regional resolution

  • Added region-prioritized release date selection from release_dates (instead of relying only on first_release_date).
  • Selection supports platform filtering (release_dates.platform.id) to avoid cross-platform date bleed.
  • Added a region-code → IGDB release-region mapping and wired ROM/config priority into metadata extraction.

• IGDB query payload updates

  • Extended game fields to fetch release date detail needed for regional selection:
    • release_dates.date
    • release_dates.region
    • release_dates.platform.id

# IGDB metadata now derives first_release_date from preferred regional candidates
"first_release_date": select_preferred_release_date(
    rom, preferred_release_regions, platform_igdb_id
)