feat(map): reverse geocode location + recenter button on dashboard and history

- Dashboard: recenter button in GPS card header (hidden until first fix)
- Dashboard: estimated location name under lat/lon via Nominatim reverse geocode (throttled 30s)
- History: recenter button fits map back to trip bounds
- Both buttons use crosshairs icon, hidden until data is available

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

templates/history.html

@@ -46,7 +46,12 @@
         <div class="card shadow-sm">
             <div class="card-header py-2 d-flex justify-content-between align-items-center">
                 <h6 class="text-primary fw-bold m-0">Route replay</h6>
-                <span id="trip-summary" class="small text-muted">Select a trip</span>
+                <div class="d-flex align-items-center gap-2">
+                    <button id="btn-recenter-history" class="btn btn-outline-secondary btn-sm" type="button" title="Recenter map" hidden>
+                        <i class="fas fa-crosshairs" aria-hidden="true"></i>
+                    </button>
+                    <span id="trip-summary" class="small text-muted">Select a trip</span>
+                </div>
             </div>
             <div class="card-body p-0">
                 <div id="history-map" aria-label="Selected trip route map"></div>