[Mobile] Add "Share air quality" from location detail sheet

src/mobile/lib/src/app/dashboard/widgets/air_quality_share_card.dart

@@ -0,0 +1,300 @@
+import 'dart:convert';
+
+import 'package:airqo/src/app/dashboard/models/airquality_response.dart';
+import 'package:airqo/src/meta/utils/colors.dart';
+import 'package:flutter/material.dart';
+
+class AirQualityShareCard extends StatelessWidget {
+  final Measurement measurement;
+  final String? fallbackLocationName;
+
+  const AirQualityShareCard({
+    super.key,
+    required this.measurement,
+    this.fallbackLocationName,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final locationName = _sanitizeText(
+      measurement.siteDetails?.searchName ??
+          measurement.siteDetails?.name ??
+          fallbackLocationName ??
+          'AirQo location',
+    );
+    final locationDescription = _sanitizeText(
+      _getLocationDescription(measurement),
+    );
+    final category = _categoryLabel(
+      _sanitizeText(measurement.aqiCategory ?? 'Unavailable'),
+    );
+    final pm25Value = measurement.pm25?.value;
+    final healthTip = _sanitizeText(
+      measurement.healthTips?.firstOrNull?.tagLine ??
+          measurement.healthTips?.firstOrNull?.description ??
+          'Stay informed and plan your outdoor time wisely.',
+    );
+    final categoryColor = _getAqiColor(measurement);
+    final isDark = Theme.of(context).brightness == Brightness.dark;
+    final cardTextColor = isDark ? Colors.white : const Color(0xFF122033);
+    final secondaryTextColor = cardTextColor.withValues(alpha: 0.72);
+    final titleFontSize = _titleFontSize(locationName);
+    final categoryFontSize = _categoryFontSize(category);
+
+    return Container(
+      width: double.infinity,
+      padding: const EdgeInsets.all(20),
+      decoration: BoxDecoration(
+        borderRadius: BorderRadius.circular(28),
+        gradient: LinearGradient(
+          begin: Alignment.topLeft,
+          end: Alignment.bottomRight,
+          colors: [
+            categoryColor.withValues(alpha: isDark ? 0.75 : 0.92),
+            AppColors.primaryColor,
+            isDark ? const Color(0xFF111827) : const Color(0xFFF4F8FF),
+          ],
+          stops: const [0.0, 0.58, 1.0],
+        ),
+        boxShadow: [
+          BoxShadow(
+            color: categoryColor.withValues(alpha: 0.22),
+            blurRadius: 28,
+            offset: const Offset(0, 14),
+          ),
+        ],
+      ),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          Row(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              Expanded(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(
+                      'AirQo',
+                      style: TextStyle(
+                        color: cardTextColor.withValues(alpha: 0.88),
+                        fontSize: 16,
+                        fontWeight: FontWeight.w700,
+                        letterSpacing: 0.2,
+                      ),
+                    ),
+                    const SizedBox(height: 10),
+                    Text(
+                      locationName,
+                      maxLines: 2,
+                      overflow: TextOverflow.ellipsis,
+                      style: TextStyle(
+                        color: cardTextColor,
+                        fontSize: titleFontSize,
+                        height: 1.02,
+                        fontWeight: FontWeight.w800,
+                      ),
+                    ),
+                    if (locationDescription.isNotEmpty) ...[
+                      const SizedBox(height: 8),
+                      Text(
+                        locationDescription,
+                        maxLines: 2,
+                        overflow: TextOverflow.ellipsis,
+                        style: TextStyle(
+                          color: secondaryTextColor,
+                          fontSize: 13,
+                          height: 1.25,
+                          fontWeight: FontWeight.w500,
+                        ),
+                      ),
+                    ],
+                  ],
+                ),
+              ),
+              const SizedBox(width: 12),
+              ConstrainedBox(
+                constraints: const BoxConstraints(maxWidth: 124),
+                child: Container(
+                  padding: const EdgeInsets.symmetric(
+                    horizontal: 12,
+                    vertical: 8,
+                  ),
+                  decoration: BoxDecoration(
+                    color: Colors.white.withValues(alpha: isDark ? 0.12 : 0.84),
+                    borderRadius: BorderRadius.circular(999),
+                  ),
+                  child: Center(
+                    child: Text(
+                      category,
+                      maxLines: 1,
+                      textAlign: TextAlign.center,
+                      overflow: TextOverflow.ellipsis,
+                      style: TextStyle(
+                        color: isDark ? Colors.white : categoryColor,
+                        fontSize: categoryFontSize,
+                        height: 1.0,
+                        fontWeight: FontWeight.w700,
+                      ),
+                    ),
+                  ),
+                ),
+              ),
+            ],
+          ),
+          const SizedBox(height: 20),
+          Row(
+            crossAxisAlignment: CrossAxisAlignment.end,
+            children: [
+              Flexible(
+                child: FittedBox(
+                  fit: BoxFit.scaleDown,
+                  alignment: Alignment.bottomLeft,
+                  child: Text(
+                    pm25Value?.toStringAsFixed(1) ?? '--',
+                    style: TextStyle(
+                      color: cardTextColor,
+                      fontSize: 72,
+                      height: 0.92,
+                      fontWeight: FontWeight.w800,
+                    ),
+                  ),
+                ),
+              ),
+              const SizedBox(width: 8),
+              Padding(
+                padding: const EdgeInsets.only(bottom: 8),
+                child: Text(
+                  'PM2.5 µg/m³',
+                  style: TextStyle(
+                    color: secondaryTextColor,
+                    fontSize: 14,
+                    fontWeight: FontWeight.w600,
+                  ),
+                ),
+              ),
+            ],
+          ),
+          const SizedBox(height: 16),
+          Container(
+            width: double.infinity,
+            padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 12),
+            decoration: BoxDecoration(
+              color: Colors.white.withValues(alpha: isDark ? 0.08 : 0.82),
+              borderRadius: BorderRadius.circular(18),
+            ),
+            child: Text(
+              healthTip,
+              maxLines: 3,
+              overflow: TextOverflow.ellipsis,
+              style: TextStyle(
+                color: cardTextColor,
+                fontSize: 14,
+                height: 1.3,
+                fontWeight: FontWeight.w600,
+              ),
+            ),
+          ),
+          const SizedBox(height: 16),
+          Text(
+            'Shared from the AirQo app',
+            style: TextStyle(
+              color: secondaryTextColor,
+              fontSize: 12,
+              fontWeight: FontWeight.w600,
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+
+  String _getLocationDescription(Measurement measurement) {
+    final siteDetails = measurement.siteDetails;
+    if (siteDetails == null) return '';
+
+    final parts = <String>[];
+
+    if (siteDetails.city != null && siteDetails.city!.isNotEmpty) {
+      parts.add(siteDetails.city!);
+    } else if (siteDetails.town != null && siteDetails.town!.isNotEmpty) {
+      parts.add(siteDetails.town!);
+    }
+
+    if (siteDetails.region != null && siteDetails.region!.isNotEmpty) {
+      parts.add(siteDetails.region!);
+    } else if (siteDetails.county != null && siteDetails.county!.isNotEmpty) {
+      parts.add(siteDetails.county!);
+    }
+
+    if (siteDetails.country != null && siteDetails.country!.isNotEmpty) {
+      parts.add(siteDetails.country!);
+    }
+
+    return parts.join(', ');
+  }
+
+  Color _getAqiColor(Measurement measurement) {
+    if (measurement.aqiColor != null) {
+      try {
+        final colorString = measurement.aqiColor!.replaceAll('#', '');
+        return Color(int.parse('0xFF$colorString'));
+      } catch (_) {}
+    }
+
+    switch (measurement.aqiCategory?.toLowerCase() ?? '') {
+      case 'good':
+        return const Color(0xFF179D5B);
+      case 'moderate':
+        return const Color(0xFFC79000);
+      case 'unhealthy for sensitive groups':
+      case 'u4sg':
+        return const Color(0xFFE17827);
+      case 'unhealthy':
+        return const Color(0xFFD63A45);
+      case 'very unhealthy':
+        return const Color(0xFF7540B5);
+      case 'hazardous':
+        return const Color(0xFF6D4C41);
+      default:
+        return AppColors.primaryColor;
+    }
+  }
+
+  double _titleFontSize(String title) {
+    if (title.length <= 12) return 30;
+    if (title.length <= 20) return 27;
+    if (title.length <= 28) return 24;
+    return 22;
+  }
+
+  double _categoryFontSize(String category) {
+    if (category.length <= 10) return 12;
+    if (category.length <= 16) return 11;
+    return 10;
+  }
+
+  String _categoryLabel(String category) {
+    switch (category.toLowerCase()) {
+      case 'unhealthy for sensitive groups':
+        return 'Sensitive Groups';
+      case 'very unhealthy':
+        return 'Very Unhealthy';
+      default:
+        return category;
+    }
+  }
+
+  String _sanitizeText(String value) {
+    if (!value.contains('Ã') && !value.contains('Â') && !value.contains('â')) {
+      return value;
+    }
+
+    try {
+      return utf8.decode(latin1.encode(value));
+    } catch (_) {
+      return value;
+    }
+  }
+}