Fetch latest available data from FDRS

[samshara]

@samshara, regarding the incomplete data from the latest available year: we can take data from the latest year, where the missing data is available. We need to indicate the year at the source info (e.g. Belize RC on FDRS, 2022, 2023, 2024) in such case.

We should not fill missing disaggregated data though (e.g. gender/age group data from different years - all these should be taken from the same year).

Originally posted by @tovari in #1396

We need to do the following:

1. Fetch Latest FDRS Data

   • Ensure all FDRS fields in CountryOverview contain the latest available data.

2. Add fdrs_ Prefix to FDRS Fields

   • Prefix all FDRS-related fields with fdrs_.

3. Add FDRS Data Year Fields

   • Create <fdrs_field>_data_year for each FDRS field.
   • For disaggregated fields (e.g., volunteers, staff):
     • Use a single year field across related groups.
     • Example:
       • Fields:
         • fdrs_male_volunteer_age_13_17, fdrs_female_volunteer_age_13_17, etc.
       • Year Field:
         • fdrs_volunteer_data_year (applies to all related entries).

4. Refactor World Bank Fields

   • Rename fields like:
     • calculated_world_bank_population_above_age_65_year → world_bank_population_above_age_65_data_year.
   • Apply this pattern to all World Bank year fields.
   • Change field type from CharField to IntField (verify prod/staging data).