feat(dashboard): wire system stats to Core API with live gauges

- Add SystemStats freezed models matching Core API response
- Add systemStatsProvider to fetch stats from /tools/system/stats
- Update dashboard to display CPU, RAM, VRAM, and disk usage gauges
- Implement color-coded gauges: green ≤50%, orange 51-75%, red >75%
- Add auto-refresh every 30 seconds
- Improve gauge widget: speedometer style, icons below labels
- Update weather widget to match air quality vertical layout

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

lib/features/front_hall/data/models/system_stats_model.dart

@@ -0,0 +1,91 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'system_stats_model.freezed.dart';
+part 'system_stats_model.g.dart';
+
+/// System statistics response from Core API.
+@freezed
+sealed class SystemStats with _$SystemStats {
+  const factory SystemStats({
+    required CpuStats cpu,
+    required MemoryStats memory,
+    required List<DiskStats> disks,
+    required NetworkStats network,
+    required GpuStats gpu,
+    required String hostname,
+    @JsonKey(name: 'queried_at') required DateTime queriedAt,
+  }) = _SystemStats;
+
+  factory SystemStats.fromJson(Map<String, dynamic> json) =>
+      _$SystemStatsFromJson(json);
+}
+
+@freezed
+sealed class CpuStats with _$CpuStats {
+  const factory CpuStats({
+    @JsonKey(name: 'usage_percent') required double usagePercent,
+    required int cores,
+    @JsonKey(name: 'load_1m') double? load1m,
+    @JsonKey(name: 'load_5m') double? load5m,
+    @JsonKey(name: 'load_15m') double? load15m,
+  }) = _CpuStats;
+
+  factory CpuStats.fromJson(Map<String, dynamic> json) =>
+      _$CpuStatsFromJson(json);
+}
+
+@freezed
+sealed class MemoryStats with _$MemoryStats {
+  const factory MemoryStats({
+    @JsonKey(name: 'usage_percent') required double usagePercent,
+    @JsonKey(name: 'total_bytes') required int totalBytes,
+    @JsonKey(name: 'used_bytes') required int usedBytes,
+    @JsonKey(name: 'available_bytes') required int availableBytes,
+  }) = _MemoryStats;
+
+  factory MemoryStats.fromJson(Map<String, dynamic> json) =>
+      _$MemoryStatsFromJson(json);
+}
+
+@freezed
+sealed class DiskStats with _$DiskStats {
+  const factory DiskStats({
+    @JsonKey(name: 'mount_point') required String mountPoint,
+    required String device,
+    required String fstype,
+    @JsonKey(name: 'usage_percent') required double usagePercent,
+    @JsonKey(name: 'total_bytes') required int totalBytes,
+    @JsonKey(name: 'used_bytes') required int usedBytes,
+    @JsonKey(name: 'free_bytes') required int freeBytes,
+  }) = _DiskStats;
+
+  factory DiskStats.fromJson(Map<String, dynamic> json) =>
+      _$DiskStatsFromJson(json);
+}
+
+@freezed
+sealed class NetworkStats with _$NetworkStats {
+  const factory NetworkStats({
+    @JsonKey(name: 'bytes_sent') required int bytesSent,
+    @JsonKey(name: 'bytes_recv') required int bytesRecv,
+    @JsonKey(name: 'bytes_total') required int bytesTotal,
+  }) = _NetworkStats;
+
+  factory NetworkStats.fromJson(Map<String, dynamic> json) =>
+      _$NetworkStatsFromJson(json);
+}
+
+@freezed
+sealed class GpuStats with _$GpuStats {
+  const factory GpuStats({
+    required bool available,
+    String? name,
+    @JsonKey(name: 'usage_percent') double? usagePercent,
+    @JsonKey(name: 'total_bytes') int? totalBytes,
+    @JsonKey(name: 'used_bytes') int? usedBytes,
+    @JsonKey(name: 'free_bytes') int? freeBytes,
+  }) = _GpuStats;
+
+  factory GpuStats.fromJson(Map<String, dynamic> json) =>
+      _$GpuStatsFromJson(json);
+}

lib/features/front_hall/presentation/providers/system_stats_provider.dart

@@ -0,0 +1,14 @@
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+import 'package:tatlock_ui/core/api/api_client.dart';
+import 'package:tatlock_ui/features/front_hall/data/models/system_stats_model.dart';
+
+part 'system_stats_provider.g.dart';
+
+/// Fetches system stats from Core API.
+@riverpod
+Future<SystemStats> systemStats(Ref ref) async {
+  final dio = ref.watch(coreApiClientProvider);
+
+  final response = await dio.get('/tools/system/stats');
+  return SystemStats.fromJson(response.data as Map<String, dynamic>);
+}

lib/features/front_hall/presentation/widgets/dashboard_content.dart

@@ -1,16 +1,45 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:tatlock_ui/features/front_hall/data/models/system_stats_model.dart';
+import 'package:tatlock_ui/features/front_hall/presentation/providers/system_stats_provider.dart';
 import 'package:tatlock_ui/shared/widgets/widgets.dart';
 import 'package:tatlock_ui/version.g.dart';
 
 /// Dashboard content shown in Front Hall when mode is dashboard.
 ///
 /// Displays system stats with gauges, weather, air quality, and version info.
-class DashboardContent extends StatelessWidget {
+/// Auto-refreshes system stats every 30 seconds.
+class DashboardContent extends ConsumerStatefulWidget {
   const DashboardContent({super.key});
 
+  @override
+  ConsumerState<DashboardContent> createState() => _DashboardContentState();
+}
+
+class _DashboardContentState extends ConsumerState<DashboardContent> {
+  Timer? _refreshTimer;
+
+  @override
+  void initState() {
+    super.initState();
+    _refreshTimer = Timer.periodic(
+      const Duration(seconds: 30),
+      (_) => ref.invalidate(systemStatsProvider),
+    );
+  }
+
+  @override
+  void dispose() {
+    _refreshTimer?.cancel();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
+    final systemStatsAsync = ref.watch(systemStatsProvider);
 
     return ListView(
       padding: const EdgeInsets.all(16),
@@ -54,37 +83,33 @@ class DashboardContent extends StatelessWidget {
         // System Stats - Gauges
         _SectionHeader(title: 'System Stats', icon: Icons.monitor_heart),
         const SizedBox(height: 8),
-        Card(
-          child: Padding(
-            padding: const EdgeInsets.all(16),
-            child: GaugeRow(
-              gaugeSize: 90,
-              gauges: [
-                GaugeData(
-                  value: 0.35,
-                  label: 'CPU',
-                  icon: Icons.memory,
-                  color: colorScheme.primary,
-                ),
-                GaugeData(
-                  value: 0.62,
-                  label: 'Memory',
-                  icon: Icons.storage,
-                  color: colorScheme.secondary,
-                ),
-                GaugeData(
-                  value: 0.78,
-                  label: 'Disk',
-                  icon: Icons.disc_full,
-                  color: colorScheme.tertiary,
-                ),
-                GaugeData(
-                  value: 0.12,
-                  label: 'Network',
-                  icon: Icons.wifi,
-                  color: Colors.teal,
-                ),
-              ],
+        systemStatsAsync.when(
+          data: (stats) => _SystemStatsCard(stats: stats),
+          loading: () => const Card(
+            child: Padding(
+              padding: EdgeInsets.all(32),
+              child: Center(child: CircularProgressIndicator()),
+            ),
+          ),
+          error: (error, _) => Card(
+            child: Padding(
+              padding: const EdgeInsets.all(16),
+              child: Row(
+                children: [
+                  Icon(Icons.error_outline, color: colorScheme.error),
+                  const SizedBox(width: 12),
+                  Expanded(
+                    child: Text(
+                      'Failed to load system stats',
+                      style: TextStyle(color: colorScheme.error),
+                    ),
+                  ),
+                  IconButton(
+                    icon: const Icon(Icons.refresh),
+                    onPressed: () => ref.invalidate(systemStatsProvider),
+                  ),
+                ],
+              ),
             ),
           ),
         ),
@@ -165,3 +190,80 @@ class _SectionHeader extends StatelessWidget {
     );
   }
 }
+
+/// Card displaying system stats with gauges.
+class _SystemStatsCard extends StatelessWidget {
+  const _SystemStatsCard({required this.stats});
+
+  final SystemStats stats;
+
+  /// Pastel colors based on usage percentage.
+  static const _pastelGreen = Color(0xFF81C784);
+  static const _pastelOrange = Color(0xFFFFB74D);
+  static const _pastelRed = Color(0xFFE57373);
+
+  /// Returns color based on usage: green ≤50%, orange 51-75%, red >75%.
+  Color _colorForUsage(double percent) {
+    if (percent <= 50) return _pastelGreen;
+    if (percent <= 75) return _pastelOrange;
+    return _pastelRed;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    // Build gauges list: CPU, Memory, GPU (if available), then all disks
+    final gauges = <GaugeData>[
+      GaugeData(
+        value: stats.cpu.usagePercent / 100,
+        label: 'CPU',
+        icon: Icons.memory,
+        color: _colorForUsage(stats.cpu.usagePercent),
+      ),
+      GaugeData(
+        value: stats.memory.usagePercent / 100,
+        label: 'RAM',
+        icon: Icons.storage,
+        color: _colorForUsage(stats.memory.usagePercent),
+      ),
+      if (stats.gpu.available && stats.gpu.usagePercent != null)
+        GaugeData(
+          value: stats.gpu.usagePercent! / 100,
+          label: 'VRAM',
+          icon: Icons.videocam,
+          color: _colorForUsage(stats.gpu.usagePercent!),
+        ),
+      // Add a gauge for each disk
+      ...stats.disks.map(
+        (disk) => GaugeData(
+          value: disk.usagePercent / 100,
+          label: _formatDiskLabel(disk),
+          icon: Icons.disc_full,
+          color: _colorForUsage(disk.usagePercent),
+        ),
+      ),
+    ];
+
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(24),
+        child: GaugeRow(
+          gaugeSize: 120,
+          gauges: gauges,
+        ),
+      ),
+    );
+  }
+
+  /// Formats disk label from mount point.
+  String _formatDiskLabel(DiskStats disk) {
+    final mount = disk.mountPoint;
+    if (mount == '/') return 'Root';
+    if (mount == '/hostfs') return 'Host';
+    if (mount.startsWith('/hostfs/')) return mount.substring(8);
+    if (mount.startsWith('/mnt/')) return mount.substring(5);
+    if (mount.startsWith('/media/')) return mount.substring(7);
+    // Return last path segment
+    final parts = mount.split('/');
+    return parts.isNotEmpty ? parts.last : mount;
+  }
+}