FB-06: always-interactive map with a recenter control

Remove the hasPoints gate on RideMap's InteractionOptions so pan/zoom
work in both the idle and recording states. Add a recenter button
(GlassPanel + IconButton, matching the existing FloatingPill/
_OverflowMenu circular-chrome pattern) shown only when follow is true
and the rider has panned away; tapping it resumes following and jumps
the camera back to the latest point or ambient position without
changing zoom.

Adds 7 widget tests covering the always-on interaction flags and the
recenter button's visibility/behavior. flutter analyze stays clean;
flutter test goes from 412 to 419, all passing.

On-device marker-pulse verification was skipped: no Android tooling
(adb/emulator) is available in this environment.

lib/src/ui/components/ride_map.dart

@@ -27,6 +27,7 @@ import '../../domain/models.dart';
 import '../../geo/geo.dart' as geo;
 import '../../tiles/tile_config.dart';
 import '../theme.dart' show ripprRadiusLarge;
+import 'glass_panel.dart';
 import 'pulsing_location_marker.dart';
 import 'skeleton_map_layer.dart';
 
@@ -267,11 +268,12 @@ class _RideMapState extends State<RideMap> with WidgetsBindingObserver {
               ? (widget.ambientPosition == null ? 2 : ambientZoom)
               : (bounds.isDegenerate ? shortRideZoom : maxTileZoom),
           maxZoom: maxTileZoom,
-          interactionOptions: hasPoints
-              ? const InteractionOptions(
-                  flags: InteractiveFlag.pinchZoom | InteractiveFlag.drag,
-                )
-              : const InteractionOptions(flags: InteractiveFlag.none),
+          // FB-06: pan/zoom must always be available, idle or recording -- the old
+          // `hasPoints` gate locked the map to `InteractiveFlag.none` whenever no trip
+          // was recording, which is exactly the "can't zoom and move around" report.
+          interactionOptions: const InteractionOptions(
+            flags: InteractiveFlag.pinchZoom | InteractiveFlag.drag,
+          ),
           onPositionChanged: !widget.follow
               ? null
               : (position, hasGesture) {
@@ -326,7 +328,43 @@ class _RideMapState extends State<RideMap> with WidgetsBindingObserver {
       ),
     );
 
-    return _sized(child: map);
+    // FB-06: the recenter control only ever makes sense once there is a `follow`
+    // mode to return to and the rider has actually panned away from it -- a static
+    // (non-following) map, like a finished ride in Trip Detail, never shows this.
+    final showRecenter = widget.follow && !_following;
+
+    return _sized(
+      child: Stack(
+        children: [
+          map,
+          if (showRecenter)
+            Positioned(
+              right: 16,
+              bottom: 16,
+              child: GlassPanel(
+                borderRadius: const BorderRadius.all(Radius.circular(999)),
+                child: IconButton(
+                  key: const Key('recenter-button'),
+                  icon: const Icon(Icons.my_location),
+                  onPressed: _recenter,
+                ),
+              ),
+            ),
+        ],
+      ),
+    );
+  }
+
+  /// FB-06: return the camera to the rider's latest known position and resume
+  /// following new updates. Zoom is left untouched -- the rider may have
+  /// deliberately zoomed in or out, and recenter should not undo that.
+  void _recenter() {
+    final ll.LatLng? target = widget.points.isNotEmpty
+        ? ll.LatLng(widget.points.last.latitude, widget.points.last.longitude)
+        : widget.ambientPosition;
+    if (target == null) return;
+    setState(() => _following = true);
+    _controller.move(target, _controller.camera.zoom);
   }
 
   /// One polyline per speed run within each segment.