feat(bibliotheque): tags et duplication profonde

Ticket #83 B1-B3 : tags JSON dénormalisés, migration Drift v19, mappings sync, helpers de filtre/suggestions, duplication profonde Program/WorkoutTemplate, tests associés.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/domain/entities.dart

@@ -334,9 +334,11 @@ final class Exercise {
     this.autoStartNextTimedStep = true,
     this.category = ExerciseCategory.uncategorized,
     this.isExample = false,
+    List<String> tags = const [],
     List<ExerciseStep> steps = const [],
     this.archivedAt,
   }) : name = _nonBlank(name, 'Exercise name'),
+       tags = normalizeTags(tags),
        imageMediaIds = _resolvedExerciseImageMediaIds(
          imageMediaId,
          imageMediaIds,
@@ -394,6 +396,7 @@ final class Exercise {
   final bool autoStartNextTimedStep;
   final ExerciseCategory category;
   final bool isExample;
+  final List<String> tags;
   final List<ExerciseStep> steps;
   final DateTime? archivedAt;
 
@@ -431,6 +434,7 @@ final class Exercise {
     bool? autoStartNextTimedStep,
     ExerciseCategory? category,
     bool? isExample,
+    Object? tags = _unchanged,
     Object? steps = _unchanged,
     Object? archivedAt = _unchanged,
   }) {
@@ -482,6 +486,7 @@ final class Exercise {
           autoStartNextTimedStep ?? this.autoStartNextTimedStep,
       category: category ?? this.category,
       isExample: isExample ?? this.isExample,
+      tags: tags == _unchanged ? this.tags : tags as List<String>,
       steps: steps == _unchanged ? this.steps : steps as List<ExerciseStep>,
       archivedAt: archivedAt == _unchanged
           ? this.archivedAt
@@ -552,8 +557,10 @@ final class Program {
     required String name,
     required this.defaultRestSeconds,
     this.isExample = false,
+    List<String> tags = const [],
     this.exercises = const [],
-  }) : name = _nonBlank(name, 'Program name') {
+  }) : name = _nonBlank(name, 'Program name'),
+       tags = normalizeTags(tags) {
     _requireNonNegative(defaultRestSeconds, 'Default rest seconds');
   }
 
@@ -561,6 +568,7 @@ final class Program {
   final String name;
   final int defaultRestSeconds;
   final bool isExample;
+  final List<String> tags;
   final List<ProgramExercise> exercises;
 
   Program copyWith({
@@ -569,12 +577,14 @@ final class Program {
     String? name,
     int? defaultRestSeconds,
     bool? isExample,
+    Object? tags = _unchanged,
   }) {
     return Program(
       metadata: metadata ?? this.metadata,
       name: name ?? this.name,
       defaultRestSeconds: defaultRestSeconds ?? this.defaultRestSeconds,
       isExample: isExample ?? this.isExample,
+      tags: tags == _unchanged ? this.tags : tags as List<String>,
       exercises: exercises ?? this.exercises,
     );
   }
@@ -769,14 +779,17 @@ final class WorkoutTemplate {
     required String name,
     this.lastStartedAt,
     this.isExample = false,
+    List<String> tags = const [],
     this.programs = const [],
     this.overrides = const [],
-  }) : name = _nonBlank(name, 'Workout template name');
+  }) : name = _nonBlank(name, 'Workout template name'),
+       tags = normalizeTags(tags);
 
   final EntityMetadata metadata;
   final String name;
   final DateTime? lastStartedAt;
   final bool isExample;
+  final List<String> tags;
   final List<WorkoutTemplateProgram> programs;
   final List<WorkoutTemplateExerciseOverride> overrides;
 }
@@ -1591,6 +1604,28 @@ String _nonBlank(String? value, String label) {
   return trimmed;
 }
 
+List<String> normalizeTags(Iterable<String> tags) {
+  final normalized = <String>[];
+  final seen = <String>{};
+  for (final tag in tags) {
+    final value = tag.trim().replaceAll(RegExp(r'\s+'), ' ').toLowerCase();
+    if (value.isEmpty) {
+      throw const DomainException('Tag must not be blank.');
+    }
+    if (value.length > 24) {
+      throw const DomainException('Tag must be 24 characters or less.');
+    }
+    if (!seen.add(value)) {
+      throw const DomainException('Tags must be unique.');
+    }
+    normalized.add(value);
+  }
+  if (normalized.length > 8) {
+    throw const DomainException('An item cannot have more than 8 tags.');
+  }
+  return List.unmodifiable(normalized);
+}
+
 List<String> _validatedImageMediaIds(List<String> ids) {
   if (ids.length > 5) {
     throw const DomainException('An exercise cannot have more than 5 images.');