fix(street-level): Panoramax UX QA — connection budget, coverage to 60 km, Esc, attribution

From a UX QA round in the browser against the live API:
- A line click could time out while coverage loaded: the meta-catalogue
  speaks HTTP/1.1 only (six connections), and six tiles plus four
  searches queued the lookup behind megabyte tiles. Tiles now take
  three connections and searches two; a search that timed out is asked
  once more.
- Between 30 and ~100 km Paris read as empty: the density grid is ~10 km
  a cell. Lines now draw to 60 km (z10), as Mapillary's do; above, dots
  grow with the pictures they stand for.
- Esc in the docked viewer collapsed the whole panel instead of clearing
  the sequence the panel says it clears (shared photo viewer: KartaView
  too). The viewer now offers Esc to the provider first; expanded, the
  dialog keeps it.
- A picture whose producer is an email address is credited to the
  instance holding it (its `via` host), so Licence Ouverte pictures name
  their source.
- Empty states say why: "no Panoramax photos here match the filters"
  when the filter hid every line, and nothing to zoom into over empty
  sea. Wording follows KartaView's ("photos", "click a line for its
  nearest photo").

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

docs/CURRENT-STATE.md

@@ -3254,9 +3254,10 @@ each picture is served by the instance holding it (OpenStreetMap France,
 IGN, MapComplete…; IGN's redirect to its OVH object storage). Its chip
 (orange, `#ff6f00`, Panoramax's own) starts off. Coverage comes from its
 vector tiles (`/api/map/{z}/{x}/{y}.mvt`, an hour's HTTP cache): sequence
-lines from z14 below 1.8 km above ground, z13 to 5 km, z12 to 12 km and z11
-to 30 km (a dense z11 tile over Paris is ~1.4 MB and 3,800 sequences; each
-tile draws its 1,600 longest), and above 30 km the `grid` layer's 0.1°
+lines from z14 below 1.8 km above ground, z13 to 5 km, z12 to 12 km, z11
+to 30 km and z10 to 60 km, as Mapillary's (a dense z10 tile over Paris is
+~2.1 MB and 8,600 sequences; each tile draws its 1,600 longest), and above
+60 km the `grid` layer's 0.1°
 density cells, binned to at most 96×96 points a tile (a z0 tile holds
 ~70,000 cells) and not counted as sequences: the panel says to zoom in. Both
 filters apply: lines carry their day and camera type, and a cell stays while