feat(offroute): MVUM legal access — pathfinder integration + places panel API + boundary_mode control

MVUM Data Import:
- Downloaded USFS MVUM Roads (150,636 features) and Trails (28,741 features)
- Imported to navi.db as mvum_roads and mvum_trails tables
- Idaho coverage: ~8,994 roads and ~4,504 trails across 7 national forests
- Preserved all vehicle-class fields (ATV, MOTORCYCLE, HIGHCLEARANCEVEHICLE, etc.)
- Preserved seasonal date ranges (*_DATESOPEN fields)

New mvum.py module:
- MVUMReader class for querying MVUM data by bbox and nearest point
- parse_date_range() for seasonal date string parsing (MM/DD-MM/DD format)
- check_access() for determining open/closed status with date checking
- symbol_to_access() fallback when per-vehicle fields are null
- get_mvum_access_grid() for rasterizing MVUM to pathfinder grid

Cost function integration:
- Added mvum parameter to compute_cost_grid()
- MVUM closures respond to boundary_mode:
  * strict = impassable (np.inf)
  * pragmatic = 5x friction penalty
  * emergency = ignored entirely
- Foot mode skips MVUM (motor-vehicle specific)

Router integration:
- Loads MVUM access grid for motorized modes (mtb, atv, vehicle)
- Tracks mvum_closed_crossings in path summary

Places Panel API:
- GET /api/mvum?lat=XX&lon=XX&radius=50
- Returns MVUM feature with access status for all vehicle classes
- Includes seasonal date ranges, maintenance level, forest/district info
- GeoJSON geometry for map display

Validation:
- MVUM places endpoint tested with Sawtooth NF road
- All four modes validated with strict/pragmatic/emergency boundary modes
- Foot mode correctly ignores MVUM restrictions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/api.py

@@ -2799,3 +2799,137 @@ def api_offroute():
     except Exception as e:
         logger.exception("Offroute error")
         return jsonify({"status": "error", "message": str(e)}), 500
+
+
+# ── MVUM Places Panel API ──
+
+@app.route("/api/mvum", methods=["GET"])
+def api_mvum():
+    """
+    Query MVUM (Motor Vehicle Use Map) features near a point.
+
+    Used by the Navi frontend places panel when a user taps near a road/trail.
+
+    Query params:
+        lat: Latitude
+        lon: Longitude
+        radius: Search radius in meters (default: 50)
+
+    Response:
+        {
+            "status": "ok",
+            "feature": {
+                "id": "FR 123",
+                "name": "Some Forest Road",
+                "forest": "Sawtooth National Forest",
+                "district": "Ketchum Ranger District",
+                "surface": "NAT",
+                "maintenance_level": 2,
+                "seasonal": "Seasonal",
+                "symbol": 2,
+                "access": {
+                    "passenger_vehicle": { "status": "Open", "dates": "06/15-10/15" },
+                    "high_clearance": { "status": "Open", "dates": "06/15-10/15" },
+                    "atv": { "status": "Open", "dates": "06/15-10/15" },
+                    ...
+                },
+                "geometry": { GeoJSON LineString }
+            }
+        }
+
+    If no MVUM feature within radius:
+        { "status": "ok", "feature": null }
+    """
+    try:
+        lat = request.args.get("lat", type=float)
+        lon = request.args.get("lon", type=float)
+        radius = request.args.get("radius", 50, type=float)
+
+        if lat is None or lon is None:
+            return jsonify({"status": "error", "message": "lat and lon required"}), 400
+
+        from .offroute.mvum import MVUMReader
+
+        reader = MVUMReader()
+        try:
+            # Try roads first, then trails
+            feature = reader.query_nearest(lat, lon, radius, "mvum_roads")
+            if feature is None:
+                feature = reader.query_nearest(lat, lon, radius, "mvum_trails")
+
+            if feature is None:
+                return jsonify({"status": "ok", "feature": None})
+
+            # Format access info
+            access = {
+                "passenger_vehicle": {
+                    "status": feature.get("passengervehicle"),
+                    "dates": feature.get("passengervehicle_datesopen")
+                },
+                "high_clearance": {
+                    "status": feature.get("highclearancevehicle"),
+                    "dates": feature.get("highclearancevehicle_datesopen")
+                },
+                "atv": {
+                    "status": feature.get("atv"),
+                    "dates": feature.get("atv_datesopen")
+                },
+                "motorcycle": {
+                    "status": feature.get("motorcycle"),
+                    "dates": feature.get("motorcycle_datesopen")
+                },
+                "4wd_gt50": {
+                    "status": feature.get("fourwd_gt50inches"),
+                    "dates": feature.get("fourwd_gt50_datesopen")
+                },
+                "2wd_gt50": {
+                    "status": feature.get("twowd_gt50inches"),
+                    "dates": feature.get("twowd_gt50_datesopen")
+                },
+                "e_bike_class1": {
+                    "status": feature.get("e_bike_class1"),
+                    "dates": feature.get("e_bike_class1_dur")
+                },
+                "e_bike_class2": {
+                    "status": feature.get("e_bike_class2"),
+                    "dates": feature.get("e_bike_class2_dur")
+                },
+                "e_bike_class3": {
+                    "status": feature.get("e_bike_class3"),
+                    "dates": feature.get("e_bike_class3_dur")
+                },
+            }
+
+            # Parse maintenance level
+            maint_level = feature.get("operationalmaintlevel", "")
+            maint_num = None
+            if maint_level:
+                # Extract first digit: "2 - HIGH CLEARANCE VEHICLES" -> 2
+                import re
+                match = re.match(r"(\d+)", maint_level)
+                if match:
+                    maint_num = int(match.group(1))
+
+            result = {
+                "id": feature.get("id"),
+                "name": feature.get("name"),
+                "forest": feature.get("forestname"),
+                "district": feature.get("districtname"),
+                "surface": feature.get("surfacetype"),
+                "maintenance_level": maint_num,
+                "seasonal": feature.get("seasonal"),
+                "symbol": feature.get("symbol"),
+                "trail_class": feature.get("trailclass"),
+                "trail_system": feature.get("trailsystem"),
+                "access": access,
+                "geometry": feature.get("geojson")
+            }
+
+            return jsonify({"status": "ok", "feature": result})
+
+        finally:
+            reader.close()
+
+    except Exception as e:
+        logger.exception("MVUM query error")
+        return jsonify({"status": "error", "message": str(e)}), 500