fix: map zoom limits configurable per-deployment via data attributes

Pi offline tiles only cover zoom 8-15; OSM live tiles support 0-19.
history.js now reads data-min-zoom/data-max-zoom from the #history-map div
instead of hardcoding 3/19. Pi template caps to 8-15 (prevents blank tiles
at extreme zooms), server template allows full 3-19 OSM range.

Co-authored-by: Copilot <[email protected]>

server/templates/history.html

@@ -56,7 +56,8 @@
             <div class="card-body p-0">
                 <div id="history-map" aria-label="Selected trip route map"
                      data-tile-url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
-                     data-tile-attrib="&copy; <a href='https://www.openstreetmap.org/copyright'>OpenStreetMap</a> contributors"></div>
+                     data-tile-attrib="&copy; <a href='https://www.openstreetmap.org/copyright'>OpenStreetMap</a> contributors"
+                     data-min-zoom="3" data-max-zoom="19"></div>
                 <div id="trip-timeline" class="border-top p-3" hidden>
                     <div class="d-flex align-items-center gap-3">
                         <button id="trip-play" class="btn btn-primary btn-sm" type="button" aria-label="Play">