feat: add tag picker in sensor calibration flow

lib/domain/models/calibration.dart

@@ -1,4 +1,4 @@
-enum CalibrationPhase { idle, ready, collecting, done, error }
+enum CalibrationPhase { idle, selectingTag, ready, collecting, done, error }
 
 const calibrationDistances = [0.5, 1.0, 2.0, 3.0];
 
@@ -14,6 +14,8 @@ class CalibrationState {
     this.avgRssi,
     this.resultRssiRef,
     this.resultPathLossExp,
+    this.tagRssiReadings = const {},
+    this.selectedTagId,
     this.error,
   });
 
@@ -28,6 +30,10 @@ class CalibrationState {
   final double? avgRssi;
   final double? resultRssiRef;
   final double? resultPathLossExp;
+  /// Latest scan RSSI per tag device ID, updated during selectingTag phase.
+  final Map<String, double> tagRssiReadings;
+  /// The tag device ID committed for this calibration session.
+  final String? selectedTagId;
   final String? error;
 
   bool get canFinish =>
@@ -47,10 +53,14 @@ class CalibrationState {
     double? avgRssi,
     double? resultRssiRef,
     double? resultPathLossExp,
+    Map<String, double>? tagRssiReadings,
+    String? selectedTagId,
     String? error,
     bool clearSelectedDistance = false,
     bool clearLatestRssi = false,
     bool clearAvgRssi = false,
+    bool clearTagRssiReadings = false,
+    bool clearSelectedTagId = false,
     bool clearError = false,
   }) =>
       CalibrationState(
@@ -66,6 +76,11 @@ class CalibrationState {
         avgRssi: clearAvgRssi ? null : avgRssi ?? this.avgRssi,
         resultRssiRef: resultRssiRef ?? this.resultRssiRef,
         resultPathLossExp: resultPathLossExp ?? this.resultPathLossExp,
+        tagRssiReadings: clearTagRssiReadings
+            ? const {}
+            : tagRssiReadings ?? this.tagRssiReadings,
+        selectedTagId:
+            clearSelectedTagId ? null : selectedTagId ?? this.selectedTagId,
         error: clearError ? null : error ?? this.error,
       );
 }