[Filtered] compacted client payload, base-layer switcher, and GeoJSON overlays

[kghbln]

Three changes to the filtered format:

• Compacted client payload (v2 serialization): per-item printouts become a positional array of {v, f, s} slots (formatted/sort values omitted when identical, value-less printouts as null), coordinates single-sourced. Decoded srfFilteredConfig −53% (3.57 → 1.68 MB on a 2,575-item page), page −37%, identical behavior. Gadgets reading srfFilteredConfig must adapt (release note included).
• map view layers parameter: multiple base layers with a Leaflet switcher. Names are leaflet-providers strings and/or custom layers defined by the Maps extension's new $egMapsLeafletLayerDefinitions (Maps 13.1+, Add egMapsLeafletLayerDefinitions setting for custom Leaflet layers ProfessionalWiki/Maps#921); without Maps, provider names still work and unknown names are skipped without breaking the map.
• map view geojson parameter: a GeoJSON overlay from a GeoJson: page or URL, fetched through the Maps extension (SSRF-guarded), simplestyle styling and popups, toggleable via the layer switcher, unaffected by the client-side filtering. With Maps absent the parameter yields an i18n'd query error and the view renders normally.

All three parts were independently pr-reviewed (report-only) with findings integrated: numeric layer names keep their configured order, malformed GeoJSON degrades to no-overlay instead of a blank map, value-filter radio DOM ids are page-unique, and GeoJSON point features use the explicitly-pathed marker icon.

[codecov]

Codecov Report

❌ Patch coverage is 67.52137% with 38 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.36%. Comparing base (7807da1) to head (bafbc7b).

Files with missing lines	Patch %	Lines
formats/filtered/src/View/MapView.php	75.75%	16 Missing ⚠️
formats/filtered/src/Filters/DistanceFilter.php	0.00%	10 Missing ⚠️
formats/filtered/src/View/MapsGeoJsonProvider.php	60.00%	6 Missing ⚠️
...filtered/src/View/MapsLayerDefinitionsProvider.php	45.45%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1133      +/-   ##
============================================
+ Coverage     58.17%   58.36%   +0.18%     
- Complexity     2435     2468      +33     
============================================
  Files           127      129       +2     
  Lines         11743    11825      +82     
  Branches        473      473              
============================================
+ Hits           6832     6902      +70     
- Misses         4566     4578      +12     
  Partials        345      345              

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[JeroenDeDauw]

LGTM. Tested locally