feat(street-level): KartaView's SINCE is its upload date, noted in the panel

KartaView's server filters by upload date only, so SINCE goes by it
throughout for KartaView: the lines (as before), the photo a click opens
and the cones, the cut-off taken as its UTC day as KartaView's startDate
(passesKartaViewFilter). Providers may declare sinceBasis: 'upload'
(validated); while one is lit the panel shows "KartaView: by upload date"
under the SINCE slider, read out with it. The gate checks the note, and
step 13's picks get 60 s on a loaded machine.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

CHANGELOG.md

@@ -116,9 +116,11 @@
   cone pointing along the drive (KartaView's own compass headings are often
   0 or far off). The IMAGERY (ALL / 360° / FLAT) and SINCE filters apply to
   KartaView as to Mapillary: its lines are filtered by KartaView's own
-  server (its filtered PNG tiles, as a mask over the JSON lines; SINCE goes
-  by upload date there), and the photo a click opens, and the cones, by
-  each photo's projection and capture date.
+  server (its filtered PNG tiles, as a mask over the JSON lines), and the
+  photo a click opens, and the cones, by each photo's projection and upload
+  date. KartaView's SINCE is the upload date (all its server can filter by);
+  a note under the slider says so while KartaView is lit (`sinceBasis:
+  'upload'` in the provider contract).
   Mapillary's line coverage and sequence cones are now shared by both
   (`lineCoverage.js`, `sequenceCones.js`).