fix(media): sélecteur de média pour les exercices (ticket #15)

Corrige/ajoute le sélecteur de média sur exercise_library_screen.dart
suite aux retours de QA. flutter analyze propre (1 warning mineur
"paramètre inutilisé" dans un test, sans impact), 27/27 tests verts,
build APK debug validé.

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

lib/presentation/exercise_library_screen.dart

@@ -1,8 +1,27 @@
 import 'package:flutter/material.dart';
+import 'package:image_picker/image_picker.dart';
 
 import '../application/application.dart';
 import '../domain/domain.dart';
 
+abstract interface class MediaSourcePicker {
+  Future<String?> pickPath(MediaKind kind);
+}
+
+final class ImagePickerMediaSourcePicker implements MediaSourcePicker {
+  const ImagePickerMediaSourcePicker();
+
+  @override
+  Future<String?> pickPath(MediaKind kind) async {
+    final picker = ImagePicker();
+    final file = switch (kind) {
+      MediaKind.image => await picker.pickImage(source: ImageSource.gallery),
+      MediaKind.video => await picker.pickVideo(source: ImageSource.gallery),
+    };
+    return file?.path;
+  }
+}
+
 final class ExerciseLibraryScreen extends StatefulWidget {
   const ExerciseLibraryScreen({
     required this.exerciseUseCases,
@@ -248,12 +267,14 @@ final class ExerciseFormScreen extends StatefulWidget {
   const ExerciseFormScreen({
     required this.exerciseUseCases,
     required this.mediaUseCases,
+    this.mediaPicker = const ImagePickerMediaSourcePicker(),
     this.exercise,
     super.key,
   });
 
   final ExerciseUseCases exerciseUseCases;
   final MediaUseCases mediaUseCases;
+  final MediaSourcePicker mediaPicker;
   final Exercise? exercise;
 
   @override
@@ -266,10 +287,10 @@ final class _ExerciseFormScreenState extends State<ExerciseFormScreen> {
   late final TextEditingController _descriptionController;
   late final TextEditingController _scoreLabelController;
   late final TextEditingController _scoreUnitController;
-  final _imagePathController = TextEditingController();
-  final _videoPathController = TextEditingController();
   String? _imageMediaId;
   String? _videoMediaId;
+  String? _selectedImageName;
+  String? _selectedVideoName;
   var _hasTime = true;
   var _hasReps = false;
   var _hasScore = false;
@@ -302,8 +323,6 @@ final class _ExerciseFormScreenState extends State<ExerciseFormScreen> {
     _descriptionController.dispose();
     _scoreLabelController.dispose();
     _scoreUnitController.dispose();
-    _imagePathController.dispose();
-    _videoPathController.dispose();
     super.dispose();
   }
 
@@ -346,19 +365,21 @@ final class _ExerciseFormScreenState extends State<ExerciseFormScreen> {
             ),
             const SizedBox(height: 8),
             _MediaImportField(
-              controller: _imagePathController,
-              label: 'Chemin de l’image',
+              label: 'Image',
+              selectedFileName: _selectedImageName,
               imported: _imageMediaId != null,
               importing: _importingImage,
-              onImport: () => _importMedia(MediaKind.image),
+              actionLabel: 'Choisir une image',
+              onPick: () => _importMedia(MediaKind.image),
             ),
             const SizedBox(height: 8),
             _MediaImportField(
-              controller: _videoPathController,
-              label: 'Chemin de la vidéo',
+              label: 'Vidéo',
+              selectedFileName: _selectedVideoName,
               imported: _videoMediaId != null,
               importing: _importingVideo,
-              onImport: () => _importMedia(MediaKind.video),
+              actionLabel: 'Choisir une vidéo',
+              onPick: () => _importMedia(MediaKind.video),
             ),
             const SizedBox(height: 24),
             Text(
@@ -461,19 +482,18 @@ final class _ExerciseFormScreenState extends State<ExerciseFormScreen> {
   }
 
   Future<void> _importMedia(MediaKind kind) async {
-    final controller = kind == MediaKind.image
-        ? _imagePathController
-        : _videoPathController;
-    final sourcePath = controller.text.trim();
-    if (sourcePath.isEmpty) {
-      _showSnackBar('Indique un chemin de fichier à importer.');
+    final sourcePath = await widget.mediaPicker.pickPath(kind);
+    if (sourcePath == null) {
       return;
     }
+    final fileName = _fileNameFromPath(sourcePath);
     setState(() {
       if (kind == MediaKind.image) {
         _importingImage = true;
+        _selectedImageName = fileName;
       } else {
         _importingVideo = true;
+        _selectedVideoName = fileName;
       }
     });
     try {
@@ -580,6 +600,11 @@ final class _ExerciseFormScreenState extends State<ExerciseFormScreen> {
     return text.isEmpty ? null : text;
   }
 
+  String _fileNameFromPath(String path) {
+    final parts = path.split(RegExp(r'[/\\]'));
+    return parts.isEmpty ? path : parts.last;
+  }
+
   void _showSnackBar(String message) {
     if (!mounted) return;
     ScaffoldMessenger.of(
@@ -635,46 +660,53 @@ final class _MeasureSwitch extends StatelessWidget {
 
 final class _MediaImportField extends StatelessWidget {
   const _MediaImportField({
-    required this.controller,
     required this.label,
+    required this.selectedFileName,
     required this.imported,
     required this.importing,
-    required this.onImport,
+    required this.actionLabel,
+    required this.onPick,
   });
 
-  final TextEditingController controller;
   final String label;
+  final String? selectedFileName;
   final bool imported;
   final bool importing;
-  final VoidCallback onImport;
+  final String actionLabel;
+  final VoidCallback onPick;
 
   @override
   Widget build(BuildContext context) {
-    return TextField(
-      controller: controller,
+    final fileName = selectedFileName;
+    final status = fileName == null
+        ? imported
+              ? 'Média déjà importé'
+              : 'Aucun fichier sélectionné'
+        : fileName;
+    return InputDecorator(
       decoration: InputDecoration(
         labelText: label,
         border: const OutlineInputBorder(),
-        suffixIcon: Row(
-          mainAxisSize: MainAxisSize.min,
-          children: [
-            if (imported)
-              const Tooltip(
-                message: 'Média importé',
-                child: Icon(Icons.check_circle_outline),
-              ),
-            IconButton(
-              tooltip: 'Importer',
-              onPressed: importing ? null : onImport,
-              icon: importing
-                  ? const SizedBox.square(
-                      dimension: 18,
-                      child: CircularProgressIndicator(strokeWidth: 2),
-                    )
-                  : const Icon(Icons.upload_file),
-            ),
-          ],
-        ),
+      ),
+      child: Row(
+        children: [
+          Icon(imported ? Icons.check_circle_outline : Icons.perm_media),
+          const SizedBox(width: 12),
+          Expanded(
+            child: Text(status, maxLines: 1, overflow: TextOverflow.ellipsis),
+          ),
+          const SizedBox(width: 12),
+          OutlinedButton.icon(
+            onPressed: importing ? null : onPick,
+            icon: importing
+                ? const SizedBox.square(
+                    dimension: 16,
+                    child: CircularProgressIndicator(strokeWidth: 2),
+                  )
+                : const Icon(Icons.upload_file),
+            label: Text(actionLabel),
+          ),
+        ],
       ),
     );
   }