feat: implement BLE provisioning protocol, rudimentary UI

lib/features/ble_provision/ble_provision_sheet.dart

@@ -1,8 +1,10 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_blue_plus/flutter_blue_plus.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
 import '../../data/sources/ble/ble_provisioner.dart';
+import '../../providers.dart';
 
 enum _Step { provision, done }
 
@@ -20,11 +22,19 @@ class _BleProvisionSheetState extends ConsumerState<BleProvisionSheet> {
   final _ssidController = TextEditingController();
   final _wifiPasswordController = TextEditingController();
 
+  late final Stream<BleScanResult> _scanStream;
+
   _Step _step = _Step.provision;
   BleScanResult? _selected;
   bool _provisioning = false;
   String? _error;
 
+  @override
+  void initState() {
+    super.initState();
+    _scanStream = _provisioner.scan();
+  }
+
   @override
   void dispose() {
     _provisioner.dispose();
@@ -40,10 +50,13 @@ class _BleProvisionSheetState extends ConsumerState<BleProvisionSheet> {
       _error = null;
     });
     try {
+      final mqttBroker = await ref.read(mqttBrokerProvider.future);
       await _provisioner.provision(
         _selected!.deviceId,
         ssid: _ssidController.text.trim(),
         wifiPassword: _wifiPasswordController.text,
+        mqttHost: mqttBroker?.host,
+        mqttPort: mqttBroker?.port,
       );
       if (mounted) setState(() => _step = _Step.done);
     } catch (e) {
@@ -88,7 +101,7 @@ class _BleProvisionSheetState extends ConsumerState<BleProvisionSheet> {
               )
             : _ProvisionStep(
                 scrollController: scrollController,
-                provisioner: _provisioner,
+                scanStream: _scanStream,
                 selected: _selected,
                 onSelected: (r) => setState(() => _selected = r),
                 ssidController: _ssidController,
@@ -102,10 +115,10 @@ class _BleProvisionSheetState extends ConsumerState<BleProvisionSheet> {
   }
 }
 
-class _ProvisionStep extends StatelessWidget {
+class _ProvisionStep extends StatefulWidget {
   const _ProvisionStep({
     required this.scrollController,
-    required this.provisioner,
+    required this.scanStream,
     required this.selected,
     required this.onSelected,
     required this.ssidController,
@@ -116,7 +129,7 @@ class _ProvisionStep extends StatelessWidget {
   });
 
   final ScrollController scrollController;
-  final BleProvisioner provisioner;
+  final Stream<BleScanResult> scanStream;
   final BleScanResult? selected;
   final ValueChanged<BleScanResult> onSelected;
   final TextEditingController ssidController;
@@ -125,27 +138,73 @@ class _ProvisionStep extends StatelessWidget {
   final String? error;
   final VoidCallback onProvision;
 
+  @override
+  State<_ProvisionStep> createState() => _ProvisionStepState();
+}
+
+class _ProvisionStepState extends State<_ProvisionStep> {
+  final _discovered = <String, BleScanResult>{};
+
   @override
   Widget build(BuildContext context) {
     return ListView(
-      controller: scrollController,
+      controller: widget.scrollController,
       children: [
         Text('Add sensor', style: Theme.of(context).textTheme.titleLarge),
         const SizedBox(height: 16),
 
-        // Scan results
-        // TODO: StreamBuilder on provisioner.scan() — show a list of
-        //       BleScanResult tiles; tapping one calls onSelected.
-        const Text('Nearby ESP32 devices'),
+        Text('Nearby ESP32 devices',
+            style: Theme.of(context).textTheme.labelLarge),
         const SizedBox(height: 8),
-        const Placeholder(fallbackHeight: 120),
+
+        StreamBuilder<BleScanResult>(
+          stream: widget.scanStream,
+          builder: (context, snapshot) {
+            if (snapshot.hasData) {
+              final r = snapshot.data!;
+              _discovered[r.deviceId] = r;
+            }
+            if (_discovered.isEmpty) {
+              return const Padding(
+                padding: EdgeInsets.symmetric(vertical: 16),
+                child: Row(
+                  children: [
+                    SizedBox.square(
+                        dimension: 16,
+                        child: CircularProgressIndicator(strokeWidth: 2)),
+                    SizedBox(width: 12),
+                    Text('Scanning…'),
+                  ],
+                ),
+              );
+            }
+            return Column(
+              children: _discovered.values.map((r) {
+                final selected = widget.selected?.deviceId == r.deviceId;
+                return ListTile(
+                  contentPadding: EdgeInsets.zero,
+                  leading: const Icon(Icons.sensors),
+                  title: Text(r.name),
+                  subtitle: Text('${r.rssi} dBm'),
+                  trailing: selected
+                      ? const Icon(Icons.check_circle,
+                          color: Colors.green)
+                      : null,
+                  selected: selected,
+                  onTap: () => widget.onSelected(r),
+                );
+              }).toList(),
+            );
+          },
+        ),
+
         const SizedBox(height: 24),
 
-        if (selected != null) ...[
-          Text('Selected: ${selected!.name}'),
+        if (widget.selected != null) ...[
+          Text('Selected: ${widget.selected!.name}'),
           const SizedBox(height: 16),
           TextField(
-            controller: ssidController,
+            controller: widget.ssidController,
             decoration: const InputDecoration(
               labelText: 'WiFi SSID',
               border: OutlineInputBorder(),
@@ -153,7 +212,7 @@ class _ProvisionStep extends StatelessWidget {
           ),
           const SizedBox(height: 12),
           TextField(
-            controller: wifiPasswordController,
+            controller: widget.wifiPasswordController,
             decoration: const InputDecoration(
               labelText: 'WiFi password',
               border: OutlineInputBorder(),
@@ -163,17 +222,18 @@ class _ProvisionStep extends StatelessWidget {
           const SizedBox(height: 16),
         ],
 
-        if (error != null)
+        if (widget.error != null)
           Padding(
             padding: const EdgeInsets.only(bottom: 12),
-            child: Text(error!,
+            child: Text(widget.error!,
                 style:
                     TextStyle(color: Theme.of(context).colorScheme.error)),
           ),
 
         FilledButton(
-          onPressed: (selected == null || provisioning) ? null : onProvision,
-          child: provisioning
+          onPressed:
+              (widget.selected == null || widget.provisioning) ? null : widget.onProvision,
+          child: widget.provisioning
               ? const SizedBox.square(
                   dimension: 20,
                   child: CircularProgressIndicator(strokeWidth: 2))