filtro por ubicación en cargas

[MARMdeveloper]

Summary

Implements location-based filtering in the Charges screen, as requested in #203.

Charges can now be filtered by location (address/geofence) using a dropdown placed
to the right of the AC/DC type filter chips. The filter supports multi-selection and
free-text search, and correctly updates the Summary card and bar charts alongside the
charge list.

Changes

ChargesViewModel.kt

• Added availableLocations: List<String> and selectedLocations: Set<String> to ChargesUiState
• Added setLocationFilter(location: String) — toggles a location in/out of the active selection
• Added clearLocationFilter() — resets the location selection
• applyFiltersAndUpdateState() now applies the location filter to the charge list, summary
  calculation and chart data so all three stay in sync

ChargesScreen.kt

• Added LocationFilterDropdown composable — a FilterChip that opens a DropdownMenu with:
  • Free-text search field to narrow down the list
  • Per-item checkmark indicating current selection
  • Menu stays open after each selection to allow multi-select
  • Clear button on the chip when one or more locations are active
  • Chip label shows the location name (1 selected), count ("N ubicaciones"), or a generic
    label when nothing is selected
• ChargesContent updated to accept selectedLocations, onLocationFilterToggled and
  onLocationFilterCleared parameters
• ChargeTypeFilterChips updated to accept an optional modifier parameter so it can
  participate in the Row layout alongside the new dropdown

res/values/strings.xml

• Added filter_location
• Added search

closes #203